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I 



PHILOSOPHICAL 

. i 


transaction s, 

4 

OF THE 

ROYAL SOCIETY 


O F 

L O N D O N. 

VOL. LXXX. For the Year 1790. 


PART I. 



LONDON, 

SOLD BY LOCK.YER DAVIS, AND PETER ELMSLTj 
PRINTERS TO THE ROYAL SOCIETY* 


MDCCXC. 







[ iii 1 


advertisement. 


WF Committee appointed by the Royal Society to direft the pub- 

T lication of the Phlofiphical TranfaiUcas, take this opportunity to 
x lication o. jr as well f rom the council-books 

acquaint the P “ b 1C> * " J from repeated declarations which have 

and journals of the that tbe printing of them was 

been made me . ' ^ of the refpective Secretaries, till 

r/onwf^ 

t 1 further in their publication, than by occaftonally recommend, ng 
felves any furth ^ ^ SecretarieS) wh en, from the particular 

the revtva rranfadions had happened for any 

circumftances of the r ^ ^ ^ ^ ^ principa! l y to have 

length of time ^ Pub i ic , that their ufual meetings 

been done wn ■ ' improvement of knowledge, and benefit of 

r grinds of Jr firR inhitution by the Royal Charters. 

and which they have ever fince Readily pur u . com- 

B„ t * Society being ot Wr-M Cotntnittee 

munications more numerous, ,t was tho g J the rs read be . 

them'’ ttfl ttf ta Inch the, fhonld judge molt Pto- 

p“t for publication in the future " d “ ScE 

done upon the 26 th of March I75 2 - Angularity of the fub- 

a«, and .ill continue to be. th< tt pretending 
jefta, o, the adrantageous manna o £ S ^ 

: t 1 t t — ■ - 

credit or judgment of their refpeaive authors. 

A 2 


It 




[ tv ] 

It is likewife neccffary on this occafion to remark, that it is an efta- 
blilhed rule of the Society, to which they will always adhere, never to 
give their opinion, as a Body, upon any fubjeft, either of Nature or Art, 
that comes before them. And therefore the thanks, which are fre- 
quently propofed from the Chair, to be given to the authors of fuch pa- 
pers as are read at their accuftomed meetings, or to the perfons through 
whofe hands they receive them, are to be confidered in no other light 
than as a matter of civility, in return for the refpeft fhewn to the Society 
by thofe communications. The like alio is to be faid with regard to 
the feveral projefls, inventions, and curiofities of various kinds, which 
are often exhibited to the Society ; the authors whereof, or thofe who 
exhibit them, frequently take the liberty to report, and even to certify 
in the public news-papers, that they have met with the higheft applaufe 
and approbation. And therefore it is hoped, that no regard will here- 
after be paid to fuch reports, and public notices ; which in fome iuftance* 
have been too lightly credited, to the dilhonour of the Society. 



\ 


\ 


\ 


CONTENTS 


O F 


VOL. LXXX. Part I. 


I. ACCO UNT of the D'fcovery of a Sixth and Seventh 
* ^7 Satellite of the Planet Saturn ; with Remarks on the 
Confruflion of its Ring, its Atmofphere, its Rotation on an 
Axis, and its Jpheroidical Figure . By William Herfchel* 
LL.D. F. R. S. Page I 

IL Agronomical Obfervations on the Planets Vi ettus and. Mars, 
made 'with a V tew to determine the heliocentric Longitude of 
their Nodes, the annual Motion of the Nodes, and the greatejl 
Inclination of their Orbits. By Thomas Bugge, F. R. S. 
Regius Profejfor of AJlronomy at Copenhagen, Member of the 
Academies of Stockholm, Copenhagen, Manheim, and Dront- 
heim, and Correjpondent of the Academy of Sciences at Paris. 

p. 21 

III. An Account of fome luminous Arches. In a Letter from 
Mr. William Hey, F. R. S. to the Rev. Jofeph Prieftley, 

LL. D. F. R. S. P- 3 Z 

IV. Extrahl of a Letter from the Rev. F. J. H. Wollauon, 

M.A.F. R. S. (dated Sydney College, Cambridge, February 
24 , 1784 ) to the Rev. Francis Wollafton, LL.B.F.R.S+ 
containing the Obfervation of a luminous Arch. p. 43 

V. An Account of a luminous Arch. In a Letter from the Rev . 
Mr. B. Hvjtchinfou to Sir Jofeph Banks, Bart. P. R. S. 

P« 45 

VI. 


'* ■ r „ rnFl of a Letter from J. Franklin, Efq. relative to a 
^ 'luminous Arch. Communicated by Sir Joieph Banks, M 

c. taz g 
Jr?£l 1 

the Noth of Ireland and Wefiern ljfands of Scotland In 
Zo Lettersfrom Abraham Mills, Efq. to John Lloyd, EJ* 

F n f)t Height of the luminous Arch which was feen on Feb. 

Cavendilh, 2§fr F. A S.andA.S. 

XI. Obfervations on Refpiration. By the Rev. Jofeph I 
w L £'I‘comt S of the Trigonometrical Operation , whereby the 

• Lf/ZlZ * * YfX:fZ r f, 

Greenwich and Paris ha, lieu ieurmmi. By Major ge « > _ 

• William Roy, F. F. S. «»« ^ 


O N T E N T S. 


A 


P P E N D X X. 


Meteorological journal left a, the Apartment, of the Royal So- 
■ M ty Order of tie Preftdent and CaumtU 


PHI- 


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THE President and Council of the Royal Society ad- 
judged, for the Year 1789, the Medal on Sir Godfrey 
Copley’s Donation to Mr. William Morgan, for his 
Two Papers on the Values of Reverfions and Survtvorflnps, 
printed in the two laft Volumes of the Philofophical 
Tran factions. 


errata. 

f, 42. The title of this Paper Ihould Hand thus: “ Extraft of a Letter from the 
Rev. F. J. H. WoUafton, M. A. F. R. 8. (dated Sydney College, 

Cambridge, Feb. 24. >7 8 4-) to Rev - Francil LUB ‘ 

F. R. S. containing the Obfervation of a luminous Arch." 

P. 93. 1 . laft, Infert “ V before “ faw” 


^ ■'$*' *^» -5-^^-£v&S 


e**3 #*£*% |S #T| £*?S2 

£**5 %„?•# <S? %«»'? «« 


PHILOSOPHICAL 


TRA N S A CTIONS 


I. Account of the "Difcovery of a Sixth and Seventh Satellite oj 
the Planet Saturn', with Remarks on the'Confiruchon of its 
Ring, its Atmofphere , its Rotation on an Axis, and itsfpheroidi- 
ccd Figure . By William Herfchel, LL.D. F. R~ S. 


Read November 1 2, 1789. 

I N a {hort Poftfcript, added to my laft Paper on Nebulae, I 
announced the difcovery of a fixth fatellite of Saturn, 
and mentioned, that I intended to communicate the particulars 
of its orbit and fituation to the Members of the Royal Society, 
at their next meeting. I have now the honour to prefent them, 
at the fame time, with an account of two fatelhtes inftead of 
one; and have called them the fixth znifeventh, though their 
Vol, LXXX. B , fituation 


A" 


2 Dr. IIerschel's Obfervatlons 

fituation in the Saturnian fyftem intitles them, very probably, 
to the fir ft and fecond place. This I have done to the end. 
that in future we may not be liable to miftake, in referring to 
former obfervations cr tables, where the five known fate Hites 
have been named according to the order they have hitherto 
been fuppofed to hold in the range of diftance from the planet. 

It may appear remarkable, that thefe fateliites fhould have 
remained fo long unknown to us, when, for a century and an 
half paft, the planet to which they belong has been the object 
of almoft every aftronomer’s curiolity, on account of the lin- 
gular phenomena of its ring. But it will be leen prefentlyv 
from the fituation and fize of the fateliites, that we could 
hardly expefl to difeover them till a telefcope of the dimenfions 
and aperture of my forty-feet reflector fhould be conftrufted ; 
and I need not obferve how much we Members of this Society 
muft feel ourfelves obliged to our Royal Patron, for his en- 
couragement of the lciences, when we perceive that the dil- 
\ 

covery of thefe fateliites is in ti rely owing to the liberal lupport 
whereby our moft benevolent Kins: has enabled his humble 

J o 

aftronomer ro complete the arduous undertaking of conftruct- 
ing this inftrument. 

The planet Saturn is, perhaps, one of the moft engaging 
objects that aftronomy offers to our view. As luch it drew 
my attention fo early as the year 1774; when, on the 17th 
of March, with a 5 ■§- feet reflector, I faw its ring reduced to 
a very minute, line, as reprefented in fig. 1. (Tab. I.) On the 
3d of April, in the fame year, I found the planet as it were 
ftYipped of its noble ornament, and dreffed in the plain fim- 
plicity of Mars. See fig. 2. I pafs over the following year, in 
which, with a 7- feet reflector, I faw the ring gradually open, 
till it came to the appearance exprelfed in fig. 3. (Tab. II.) the 

5 original* 


on the Planet Saturn . 

3 

original of which was delineated from nature, on the 20th 
of June, i" 83 , by means of a very good 10-feet reflector. 

It fhould be noticed, that the black dilk, or belt, upon the 
ring of Saturn is not in the middle of its breadth; nor is the 
ring fubdivided by many fuch lines, as has been reprefented 
-in divers treatifes of aftronomy ; but that there is one fin°-ie, 
dark, confiderably broad line, belt, or zone, upon the ring, 
which I have always permanently found in the place where 
my figure reprefeuts it. I give this,, however, only as a view 
of the northern plane .of the ring, as the fituation of the 
planet has hitherto not afforded me any other. The fouthem 
one, which is lately come to be expofed to the fun, will 
fhortly be opened fufficiently to enable me to give a!fo the 
fituation of its belts, if it fhould have anv. 

From my obfervations it appears, that the zone on the 
northern plane of the ring is not, like the belts of Jupiter or thofe 
of Saturn, fubjecl to variations of colour and figure; but is moft 
probably owing to fome permanent conftruCtion of the furface 
of the ring itfelf. That however, for in fiance, this black belt 
cannot be the (hadow of a chain of mountains, may be gathered 
from its being vifible.all round on the ring; for at the ends of 
the anfae tnere could be no (hades vifible, on account of the 
direction of the fun’s illumination, which would be in the line 
of the chain ; and the fame argument will hold good againft 
fuppofed caverns or concavities. It is moreover pretty evident,, 
that this dark zone is contained between two concentric circles, 
as all the phenomena anfwer to the projection of fuch a zone. 
Thus, in fig. 4. which was taken the nth of May, 1780, 
we may fee, that the zone is continued all round the ring, 
with a gradual 4 ecreafe of breadth towards the middle, 

B 2 anfwering 


. Dr. Herschel’s Obfervations 

^nfwering to the appearance of a narrow circular plane, pro- 
jected into an ellipfis. 

As to the furmife, which might occur to us, of a diviiion 

of the ring, or rather of two rings, one about the other, with 

a diftance of open fpace between them, it does not appear eli- 

oible to venture on fo artificial a conftru&ion, by way of ex- 
^ , 
plaining a phenomenon that does not abfolutely demand it. 

If one ring, of a breadth fo confiderable as that of Saturn, 
is juftly to be efteemed the moft wonderful arch that, by the 
laws of gravity, can be held together, how improbable muft 
it appear to fuppofe it fubdivided into narrow flips of rings, 
which by this feparation will be deprived of a fufficient depth, 
and thus lofe the only dimenfion which can keep them from 
falling upon the planet ? It is however true, that as yet we do 
not know of the rotation of the ring, which may be of luck 
a proper velocity as greatly to affift its ftrength ; and that, in 
the fubdivilions, of courfe the different velocities for each di- 
vifion may be equally fuppofed to keep them up. If the fouthem 
plane fhould prove to be very differently marked, it will at 
once remove every furmife of luch a diviiion ; but if it fhould 
offer us the fame appearance of a dark zone, in the lame fitua- 
' tion, and of an equal breadth with the one I have obferved oil 
the northern fide, I would ftill remark, that, fince a moft effec- 
tual way to verify the duplicity of the ring is within our 
reach, it will be the heft way to fufpend our judgement till 
that can be put to the trial. The method I allude to is an 
occultation of fome confiderable ftar by Saturn, when, if the 
ring be divided, it will be feen between the openings, as well 
as between the ring and Saturn. 

With regard to the nature of the ring, we may certainly 

affirm, that it is no lefs folid and lubftantial than the planet 

itfelf. 


cm the Planet Saturn. 5 

jtfelf. The fame reafons which prove to us the folidity of tne 
one will be full as valid when applied to the other. Thus we 
fee, in fig. 3. and 4. the fhadow of the body of Saturn upon 
the ring, which, in fig. 3. is eclipfed towards the north, on 
the following fide, and in fig. 4. about the middle, according 
to the oppofite fituation of the fun. In the fame manner we 
fee the (hadow of the ring caft on tne planet, wheie in fig. 1. 
and 2. we find it on the equatorial part; and May 28, 1780, 

I faw it towards the fouth. If we deduce the quantity ot 
matter, contained in the body, from the power whereby the 
fatellites are kept in their orbits, and the time of their revolu- 
tion, it muft be remembered, that tne ring is included in the 
refult. It is alfo in a very particular manner evident, that 
the ring exerts a confiderable force upon thefe revolving bodies, 
fince we find them ftrongly affedled with many irregularities in 
their motions, which we cannot properly afcribe to any other 
caufe than the quantity of matter contained in the ring ; at leaft 
we ought to allow it a proper fhare in the efifedl, as we do not 
deny but that the confiderable equatorial elevation of Saturn, 
which l {hall eftablifh hereafter, muft alfo join in it. 

The light of the ring of Saturn is generally brighter than 
that of the planet: for inftance, April 19, 1 777 ’ ^ law the 
fouthern part of the ring, which pafled before the body, very 
plainly brighter than the difk of Saturn, on which it was pro- 
jefted ; and on the 27th of the fame month, I found, that 
with a power of 410, my feven-feet reflector had haidly light 
enough for Saturn, when the ring was notwithstanding fuffi- 
ciently bright. Again, the 11th of Marco, 1780, I tried the 
powers of 222, 332 , and 449* fucceftively, and found the 
light of Saturn lefs intenfe than that of the ring ; the colon 1 

of the body with the high powers turning to a kind of yellow, 
„ while 


6 Dr. Hersciiel’s Obfcrvations , 

while that of the ring ftill remained white. The fame rcfulr 
happened on June 25, 1781, with the power 460. 

I come now to one of the raoft remarkable properties in the 
-conftru&ion of the ring, which is its extreme thinnefs. The 
fituation of Saturn, for fome months pad, has been particu- 
larly favourable for an inveftigation of tins circumftance ; and- 
my experiments have been fo complete, that there can remain 
no doubt on -this head. 

When we were nearly in the plane of the ring, I have- 
repeatedly feen the firft, the fecond, and the third fatellites 
nay even the fixth and leventh, pals before and behind the 
ring in fuch a manner that they ferved as excellent microme- 
ters to eftimate its thicknefs by. It may be proper to men- 
tion a few indances, efpecially as they will lerve to folve iome 
phenomena that have been remarked by other aftronomei>, 
without having been accounted for in any manner that could 
be admitted, confidently with other known fads. July 18, 
1789,, at 19 h. 4 1' 9", lidereal time, the firft fatellite deemed 
to hang upon the following arm, declining a little towards the 
north, and I faw it gradually advance upon it towards the 
body of Saturn.; but the ring was not lo thick as the lucid 
point. July 23, at 19 b. 4T S ', the fecond fatellite was a 
very little preceding the ring ; but the ring appeared to be lefs 
than half the thicknefs of the fatellite. July 27, at 20 h. 
1 12! \ the fecond fatellite was about the middle, upon the 
following arm of the ring, and towards the fouth ; and the 
fixth fatellite on the farther end, towards the north; but the 
arm was thinner than either of them. Auguft 29, at 22 h. 
i.2 / 25", the third fatellite was upon the ring, near the end of 
* the preceding arm ; and my remark at the time when I faw it 
was, that the arm deemed not to be the fourth, at ieaft not the 
thirds part of the diameter of the fatellite, which, in the 

fituation 


on the Planet Saturn , 7 ' 

fTtuarion it was, I took to be lefs than one Angle fecond in dia- 
meter. At the fame time I alfo faw the feventh fatellite, at a- 
lirttle diftance following the third, in the fhape of a bead upon, 
a thread, projecting on both tides of the fame arm \ hence we 
are fure, that the arm alfo appeared thinner than the feventh- 
fatellite, which is- confiderably (mailer than the (ixth, which 
again h a little lefs than the firft fatellite. Auguft 31, at 
20 h. 4s 7 26'', the preceding arm was loaded about the middle 
by the third fatellite. October 1 5, at oh; 43" 44 // » I ^ aw ^ ie 
fixth fatellite, without obftrudlion, about the middle of the 
preceding arm, though the ring was but barely vifible with 
mv forty-feet reflector, even while the planet was in the meri- 
dian ; however, we were then a little inclined to the plane of 
the ring, and the third fatellite, when it came neai its con- 
junction with the firft, was fo fituated that it muft have partly 
covered the firft a few minutes after the time I loft it behind' 
my houfe. In all thele obfervations the ring did not in the 
lead interfere with my view of the fatelhtes. October 16, I 
followed the fixth and feventh fatellites up to the very di(k of 
the planet; and the ring, which was extremely faint, oppofed/ 
no manner of obftruChon to my (eeing them gradually ap- 
proach the di(k, where the feventh vamfhed at 21 h. 46 44 9- 

and the fixth at 22 h. 16' 44'A 

I might bring many other inftances, if the above were not 
quite fufficient for the purpofe. , 1 here is, however, fome 
confiderable fufpicion, that, by a refraCfion tnrough fome very 
rare atmofphere on the two planes of the ring, the fatellites- 
might be lifted up and deprefi'ed, fo as to become vifible on 
both fides of the ring, even though the ring fhould be equal in*, 
thicknefs to the diameter of the fmalleft fatellite, which may 

amount to a thoufand miles. As for the argument of its., 

^credible. 


& Dr. Herschel’s Obfervatjom 

incredible thinnefs, which forae aftronomers have brought 
from the fliort time of its being invihble, when the eartli 
pafles through its plane, we cannot fet much value upon them ; 
for they muft have fuppofed the edge of the ring, as they have 
alfo reprefented it in their figures, to be fquare ; but there is 
the greateft reafon to fuppofe it either fpherical or fpheroidical, 
in which cafe evidently the ring cannot difappear for any long 
time. Nay, I may venture to fay, that the ring cannot polli- 
bly difappear on account of its thinnefs ; imce, either from the 
ed<re or the fides, even if it were fquare on the corners, it 
muft always expofe to our fight fome part which is illuminated 
by the rays of the fun : and that this is plainly the cafe, we 
may conclude from its being vifible in my telefcopcs during 
the time when others of lels light had loft it, and when evi- 
dently we were turned towards the unenlightened tide, fo that 
we muft either fee the rounding part of the enlightened edge, 
or elfe the refieftion of the light of Saturn upon the fide of the 
darkened ring, as we fee the reflected light of the earth on the 
dark part of the new moon. 1 will, however, not decide 
which of the two may be the cafe; efpecially as there aie 
other very ftrong real'ons to induce us to think, that the edge 
of the ring is of fuch a nature as not to reflect much light. 

I cannot leave this fubjeft without mentioning both my own 
former furmifes, and thofe of feveral other aftronomers, of a 
fuppofed roughnefs in the furface of the ring, or inequality m 
the planes and inclinations of its flat fides. They arote.from 
feeing luminous parts on its extent, which were fuppofed to be 
projecting points, like the moon’s mountains; or from feeing one 
arm brighter or longer than another ; or even from feeing one 
arm when the other was invifible. I was, in the beginning of 
this feafon, inclined to the fame opinion, till one of thefe iup- 


on the Planet Saturn . 9 

pofed luminous points was kind enough to venture 08 tne edge 
of the ring, and appeared- in the fhape or a latellite. Now, as 
I had collected every inequality ot this iort, it was eaiy enough 
for me afterwards to calculate all luch turmiles by tne known 
periodical time of the firft, fecond, third, fixth, and feventh 
Satellites ; and I have always found that fuch appearances were 
owing to’fome of thefe fatellites which were either before or 
behind the ring. The 20th of October, for inftance, at 
22 h. 35' 46", 1 faw four of Saturn’s fatellites all in one row, 
and at almoft an eqnal diftance from each other, on the fol- 
lowing fide ; and yet the firft latellite, which was the fartheft 
of them all, was only about half-way towards its greateft elon- 
gation from the body of Saturn, as may be feen in fig- 5 - ( Tab * 
in.). How eafily, with an inferior telefcope, this might have 
been taken for one of the arms of Saturn, Ileave thole to gueis 
who know what a degree of accuracy it muft require to diftm- 
guifh objects that are fo minute, and at the fame time lb faint, 
on account of their nearnefs to the difk of the planet. Upon 
the whole, therefore, I cannot fay, that I had any one inftance 
that could induce me to believe the ring was not of an uniform 
thicknefs ; that is, equally thick at equal diftances from the 
center, and of an equal diameter throughout the whole of its 
conftrudtion. The idea of protuberant points upon the ring 
of Saturn, indeed, is of itfelf fufficient to render the opinion ot 
their exiftence inadmiffible, when we confider the enormous 
fize fuch points ought to be of, for us to fee them at the dif- 

tance we are from the planet* 

From thefe fappofed luminous points I am, by impercep- 
tible fteps, brought to the difcovery of two fatellites of Saturn, 
which had efcaped unnoticed, on account of their little diftance 
from the planet, and faintnefs ; which latter is partly to be 

Vol. LXXX. ' C afcribed 


,0 Dr. Herschel’s Obfervations 

afcribed to their fmallnefs, and partly to being fo near the 
light of the ring and diik of Saturn. Strong fufpicions ot 
the esiftcnce of a fixth fatellite I have long entertained ; and, 
if I had been more at leifure two years ago, when the d.ico- 
very of the two Georgian fatellites took me as it were off the 
fcent, I fhould certainly have been able to announce its exift- 
ence as early as the 19th of Auguft, >787,' when, at tib> 
I*/ S 6 ", I faw, and marked it down as being probably, a 
fixth fatellite, which was then about 12 degrees paft its greateft 
preceding elongation. But, as 1 obferved before, not having 
time to give my thoughts to the fubject, 1 relerved a full m- 
veftigation of the number of fatellites, and the nature or the 
rino- of Saturn for a future opportunity. B Ji ks, not having 
tmy tables of the fatellites, 1 could not confidently lay, whether 
the fifth fatellite was not one of the live which 1 perceived m 
motion that night, though afterwards I found, that the nal 
fifth had alio been in view, and was marked down as a U .r, 
by the letter b, in a figure 1 delineated of datum and *» Utel- 

lites that evening. 

In the year 1788 very little could be done towards a diico- 
very, as my twenty-feet fpeculum was lo much tarmlhed by 
% enith [weeps, in which it had been more than utually expoted 
to falling dews, that I could hardly fee the Georgian l.udhus. 
In hopes of great fuccefs with my forty-feet ipeculum, I de- 
ferred the attack upon Saturn till that fhould be timlhed ; and 
having taken an early opportunity of direaing it to Saturn, 
the very firft moment I faw the planet, which was the 28th 
of laft Auguft, I was prefented with a view of fix of its iatel- 
lites, in fuch a fituation, and fo bright, as rendered it impol- 
fi'ble to miftake them, or not to fee them. Trie retrogra e 

motion of Saturn amounted to nearly 4i minutes per ay, 

„ which 

7 


on the Planet Saturn. 1 1 

which made it very eafy to atcertain whether the ftais I took 
to be fatellites really were fo ; and, in about two hours and an 
half, I had the p'leafure of finding, that the planet had vifibly 
carried them all away from their places. I continued my ob- 
fervations conftantiy, whenever the weather would permit ; and 
the creat light of the forty-feet fpeculum was now of fo much 
ufe,°that I alfo, on the 17th of September, detected the 
feventh Satellite, when it was at its greateft preceding elon- 


As foon a's I had obfervations enough to make tables of the 
motion of thefe new fatellites, I calculated their place back- 
wards, and foon found that many fuipicions of thefe fatellites, 
in the lhape of protuberant points on the arms, were con- 
firmed, and ferved to correct the tables, lo as to render them 
more perfeft. Fig. 6. reprefents the feven fatellites of Saturn, 
as they were fituated October a 8, at 21 h. 22" 45". The 
fmall ftar s ferved to lhew the motion of the planet in a fti ik- 
ing manner; as, in about 3 1 hours after the above-mentioned 
time, the whole Saturnian fyftem was completely moved away, 
fo as to leave the ftar s as much following the fecond and firft. 
fatellites, which then were in conjunction, as it now was before 


the fecond. . 

By comparing together many obfervations of the fixth latel- 

lite, I find, that it completes a fidereal revolution about Sa- 
turn in one day, 8 hours, 53' 9" And if we fuppofe, with M. 
DE LA Lande *, that the fourth is at the mean diftance of 3 
from the center of Saturn, and performs one revolution m 
1 5 d. 22 h. 34' 38", we find the diftance of the fixth, by 
Kepler’s law, to be 35", 058. Its light is confiderably ftrong, 
but not equal to that of the firft fatellite, loi, on the 20th of 


* Alh*. § 2996, 2997. 

C z 


October, 


12 Dr. Herschel’s Obfervations 

Caober, at 19 h. 56' 46", when thefe two fatellites were 
placed as in fig. 7. the firft, notwithftanding it was nearer the 
planet than the fixth, was (till vifibly brighter than the latter. 

It would, however, be worth while to try whether a good 
achromatic telefcope, of a large aperture, might not poifibiy 
(he;v it at the time of its greateft diftance from the planet, 
and when no other fatellite is near; that is, provided it will 
(hew the other five fatellites with great eafe, asotherwife there 
will be no reafon to expedt it Ihould Ihew the fixth. 

In the period of this fatellite I have employed the obferva- 
tion of the 19th of Auguft, 1 7 ^ 7 ’ as ’ * roin °ther calcula- 
tions, it feems the revolution is determined near enough to 

reach back fo far. 

The moft diftant obfervations of the feventh fatellite, being 
compared together, Ihew, that it makes one fidereal revolution 
in 22 hours, 40 minutes, and 46 feconds : and, by the lame 
data which ferved to afeertain the dimenfion of the orbit of 
the fixth, we have the diftance of the feventh, from the cen- 
ter of Saturn, no more than It is incomparably fmal- 

ler than the fixth ; and, even in my forty-feet reflector, ap- 
pears no bigger than a very fmall lucid point. I lee it, how- 
ever, alfo very well in the twenty-feet refloftor ; to which the 
exquifite figure, of the Ipeculum not a little contributes. It 
muft neverthelefs be remembered, that a fatellite once dilco- 
. vered is much eafier to be leen than it was before we were 
acquainted with its place. 

The revolution of this fatellite is not nearly fo well afeer- 
tained as that of the former.. The difficulty oi having a num- 
ber of obfervations is uncommonly great ; for, on account of 
the fmallnefs of its orbit, the fatellite lies generally before and 

behind the planet and its ring, or at leaft fo near them that, 

except 


on the Planet Saturn . 


*3 


except in very fine weather, it cannot eahly be feen well 
enough to take its place with accuracy. On the other hand, 
the greateft elongations allow fo much latitude for miftaking 
its true fituation, that it will require a confiderable time to 
divide the errors that muft arife from imperfedl eftimations. 

The orbits of tnefe two latellites, as appears from many 
obfervations of them, are exaftly in the plane of the ring, or 
at leaft deviate fo little from it, that the difference cannot be 
perceived. It is true, there is a poffibility that the line of 
their nodes may be in, or near, the prefent greateft elongation, 
in which cafe the orbits may have fome fmall inclination ; but 
as I have repeatedly feen them run along the very minute arms 
of the ring, even then the deviation cannot amount to more 
than perhaps one or two degrees; if, on the contrary, the 
nodes fhould be fituated near the coujundtion, this quantity 
would be fo confiderable that it could not have efcaped my 
obfervation. 

From the ring and Satellites of Saturn we now turn oui 


thoughts to the planet-, its belts, and its figure. 

April 9, * 775 * I obferved a northern belt on Saturn, which 
was a little inclined to the line of the ring. 

May 1, 1776. There was another belt, inclined about 15 de- 
grees to the fame line, but it was more to the 
louth, and on the following fide came up to the 
place in which the ring crofles the body. 

July I3> The belt was again depreffed towards the 

north, almoft touching the line where the ring 
paflfed behind the body. 

April 8, 1777. There were two fine belts, both a little in- 
clined to the ring. 

June 


H 

June 20, 


May 1 1 , 

I 

22 , 

— 2 3’ 
Jan. 21, 

22 , 

May 17, 

— 2 3> 
June 19, 


June 20, 
— 21, 


Dr. IIersciiel’s Obfervhtions 

1778. There were two belts parallel to the ring; 
but the northern one had fome faint, cloudy 
appearance, towards the preceding, or wefdern fide. 

1779. Two equatorial belts. 

A bright belt over a dark one. 

One dark, and one very faint white belt. 

A dark belt, and a pretty bright white one. 

1780. Two belts ; the mold north clouded. 

Faint belts, 

A dark, equatorial belt. 

A fdrong, equatorial belt. 

at 10 h. 15', With a new, excellent feven-feet fpe- 
culum, I fee two belts, and a cloudy appearance, 
which is not come up to the middle ; but, it is 
a large figure, fome part of it is already paid the 
center fithis is, provided Satuin turns upon its axis 
the fame way as Jupiter does). See fig. 8. where 
the ring is omitted. 

1780. 1 oh. io\ The fame figure is on the difk, but 
feems to be more central than it was yefterday. 

9 h. 25', The fame two belts; a idrong, dark fpot, 
near the margin of the difk ; fee fig. 9. ; ring not 
exprefl'ed. 

1 o*h , T, The fpot not fo remarkable as it was at 


9 n 


26, Small twenty-feet telefcope ; an equatorial belt, and 


another lefs marked. 

29, Two dark equatorial belts. 

April 19, Two belts. 

Auguft 23, Two belts, a little declining from the equatorial 


pofition. 


Auguft 


on the Planet Saturn. j % 

Auouft 26, A broad belt much inclined ; With 200, 250, 
•500, 400, faint appearances of a fecond and of a 

third belt. 

27, The belts lefs inclined. 

Sept* 2, A darkifh belt, but very little inclined ; and a fine 
white belt, clofe to the ring, 

5, The belt a little inclined. 

6, The belt not inclined. 

_ 8, The bright belt clofe to the ring, and two dark equa- 
torial belts. 

It will not be neceffarv to continue the account of thefe 
belts up to the prefent time; but I have conftantly obferved 
them, and found them generally in equatorial fituations, though 

now and then they were otherwife. 

We may draw two conclufions from what has been reported. 
The firft, which relates to the changes in the appearance of 
the belts, is, that Saturn has probably a very confiderable atmo* 
fphere, in which thefe changes take place ; juft as the alteia- 
tions in the belts of Jupiter have been fhewn, with great pro- 
bability, to be in his atmofphere. This has alfo been con* 
firmed by other obfervations : thus, in occultations of Saturn s 
Satellites, I have found them to hang to the difk a long while 
before they would vanifh. And though we ought to make fome 
allowance for the encroachment of light, wnereby a fatellite 
is feen to reach up to the difk fooner than it actually does, 
vet, without a confiderable refraction, it could hardly be kept 
fo long in view after the apparent contaCt. The time of 
hanging upon the dilk, in the feventh fatellite, has actually 
amounted to 20 minutes. Now, as its quick motion during 
that interval carries it through an arch of near fix degrees, we 

find, that this would denote a refraClion of about two feconds, 

provided 


jg Dr. Herschel’s Obfervations 

provided the encroaching of light had no fhnre in the efTefh 
By an obfervation of the fixth fatellite, the refraction of Sa- 
torn’s atmofphere amounts to nearly the fame quantity ; for this 
fatellite remained about 14 or 15 minutes longer in view than 
it fhould have done; and as it moves about 2$ degrees m that 
- time, and its orbit is larger than that of the leventh, tne 
difference is inconfiderable. It is not my prefent intention to 
enter into a confideration of the amount of thefe retractions, 
otherwife we might perhaps find data enough tofubjeCt them to 
fome calculation. But what has been laid will lufficc to (hew, 
that very probably Saturn has an atmofphere of a confiderablc 

denfity. 

The next inference we may draw from the appearance ct 
the belts on Saturn is, that this planet turns upon an axis which 
is perpendicular to the ring. The arrangement of the belts, 
during the •courfe of fourteen years that I have oblerved them, 
has always followed the direction of the ring, which is what 
I have called being equatorial. I hus, as the ring opened, the 
belts began to advance towards the louth ; and to (hew an in- 
curvature anfwering to the projection of an equatorial line, or 
to a parallel of the fame. When the ring doled up, they 
returned towards the north ; and are now, while the ring paffes 
over the center, exadly ranging with the fhadow of it on the 
body; generally one on each fide, with a white belt clofe to 
it. When I fay, that the belts have always been equatorial, 
I pafs over trifling exceptions, which certainly were owing to 
local caufes. The ftep from equatorial belts to a rotation on ail 
axis is fo eafy, and, in the cafe of Jupiter, fo well afcertained, 
that I fhall not hefitate to take the fame confequence for granted 
here. But, if there could remain a doubt, the obfervations of 


on the Planet Saturn . i y 

lime 19, 20, and 2T, zy So, where the fame fpot was feen In 
three different fltuations, would remove It completely. 

There is another argument, of equal validity with the for- 
mer, which now I fhall bring on. It is founded upon the fol- 
lowing ohfervations, and will fhew that Saturn, like Jupiter, 
Mars, and the Earth, is flattened at the Poles ; and therefore 
ought to be fuppofed to turn on its axis. 

July 22, 1776. I thought Saturn was not exadtly round. 

Mav 31, 1781. It appears as if the body of Saturn was at 
leaft as much flattened as that of Jupiter; but as 
the ring interferes, this may be better afcertained 
eight years hence. 

Auguft 18, 1787. The body of Saturn is of unequal diame- 
ters, the equatorial one being the longeft. 

Sept. 14, 1789, 23 h. 36' 32". Having referved the exami- 
nation of the two diameters of Saturn to the pre- 
fent as the moil: favourable time, Imeafured them 
with my twenty-feet refledtor, and a good parallel- 
wire micrometer. 

t) 

Equatorial diameter, 1 ft meafure, 21,94 

2d • • * 23,1 1 

3 d . . . 21,73 

4th . . 22,85 

H 

Mean 22,81 

Polar diameter, I ft meafure, 20,57 

2d . . . 20,10 

3d . . . 21,16 

Mean 20,6s 

d % 


Vol. LXXX. 


1 


Dr . Hekschel’s Obfervations 

By this it appears that Saturn is confiderably flattened at 
the poles. And as the greateft meafures were taken id the lme 
of the ring and of the belts, we are allured that the axis o 
the planet is perpendicular to the plane of the ring; and 
that the equatorial diameter is to the polar one nearly as 1 1 

t0 \Ve may alfo infer the real diameter of Saturn from thefe 
meafures, which are perhaps more to be depended upon than 
any that have hitherto been given. But as m my journal I 
have meafures that were repeatedly taken thefe ten years pall, 
not only of the diameter of Saturn, but of tire ring, and its 
opening, whereby its inclination may be known ; a. well at of 
X diftance of the fourth, and fifth, and other fatellites, 
which will be of great ufe in afeertaining the quantity of mat- 
ter contained in the planet, 1 referve a full mveftigauon o 
thefe things for another opportunity; hnce, from the date o 
this Paper, it will be fufficiently evident, that there can be no 
time for me to enter properly into the tubject. 

One beautiful obfervation of thetranfitof the fhadow of the 
fourth fatellite over the dilk of Saturn, 1 muft add, to con- 
clude this Paper. . . 

Laft night, November 2, 1789, at 23 h. 13 fu.ereal turn, 

being always in queft of any appearance that may a or t re 
means of afeertaining the rotation of Saturn on an axis, I 
difeovered a black fpot on the following margin of the dilk 

of that planet. 

At 22 h. 21', I perceived a protuberance on the louth pre- 
ceding edge of the dilk, which I fuppofed to be the fourtu 

fatellite going to emerge. 

At 


I 


on the Planet Saturn, ip 

At 23', I found that the black fpot had advanced a little 
towards the preceding fide. 

At 30% with a power of 300, I found it ftill advancing, 
and faw that the fpot was a little to the north of the equatorial 
belt, but fo that a fmall part of it was upon the belt. 

At 3J 7 , the black fpot was a little more than one-eighth of 
the diameter of Saturn advanced from the following edge 
towards the center. 

At 39', the fatellite was detached. 

At 49', the fpot was advanced fo as to be about one-third of 
its way towards the center; and the fourth fatellite near half 
its own apparent diameter clear of the edge. 

In this fituation of the planet I took an eye-draught of it, (fee 
fig. 10.) as it appeared with the black fpot on the belt ; the lately 
emerged fourth fatellite ; two parallel dark belts, the inter- 
mediate fpace between them and the equatorial one being a little 
brighter than the reft of the difk ; the fixth, third, and fecond 
fatellites on the preceding fide ; the ring projecting like two 
very (lender lines on each fide of the dilk, and containing the 
firft fatellite upon the following arm, with the fifth at a con- 
fiderable diftance following. 

At o h. 5", the black fpot was got a little more than half 
way towards the center. It was much darker than the belt, 
and more upon it than before. 

At 1 h. 2', by advancing gradually towards the fouth, it 
was now almoft intirely drawn upon the equatorial belt. 

At 1 h. 13', the black fpot approached towards a central 
fituation. 

At 1 h. 21' 5i r/ , it was perfectly central, and at the fame 
time upon the middle of the equatorial belt. 

D 2 


I followed 


Dr. Herschel’s Obfervations , Sec. 

20 1 followed the foadow of the fatellite with great attention 
up to the center, in order to fecure a valuable epocha, which 
* ay ferve to improve our tables of the mean motion of this 

fatellite. 

itttT T TATV/T up'R^CHEL. 


Slough, near Windfor, 
November 3, 1729* 



Ph ilos.Tran &. Vol. J . X X X . Tab. jp. zo . 



Marchjj.i'jj4 










v 


. -V. 






Philos-Trans. Vol. LXXX. Tab. II. />. 20. 




% ^ 





t 


I 




/ 


✓ 



\ 


I 


) 

) 







/ 



I 


, > 


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[ 21 ] 


II. Agronomical Obfervations on the Planets Venus and Mars, 
'made with a View to determine the heliocentric Longitude of 
their Nodes, the annual Motion of the Nodes, and the great efi 
Inclination of their Orbits. By Thomas Bugge, F. R. S. 
Regius Profejfor of Aftronomy at Copenhagen, Member of the 
Academies of Stockholm, Copenhagen, Manheim, and DronO 
heim, and Correfpondeni of the Academy of Sciences at Paris. 


Read November 26, 17^ 9 * 


I. The heliocentric longitude and annual motion of Venus s nodes . 

T HE following agronomical obfervations were made at 
the Royal Obfervatory at Copenhagen with a fix-feet 
tranfit inftrument, and with a mural quadrant of fix-feet 
radius. It would be too tedious to enumerate all the original 
obfervations, which either are already printed, in the firft 
volume of my Agronomical Obfervations, or will very foon 
be publiflied in the fecond volume. 'I only fliall fet down tne 
obferved geocentric longitudes and latitudes, corrected for aber 
ration and nutation, and compared with the tables of Dr. 
Halley and of M. de la Lande. 


Mean 


Profejfor Bugge’s Agronomical Obfcrvalion: 


22 


Mean time at 
Copenhagen. 

Obferved 
geocentric 
longitude 
of ? . 

Obferved 
geocentric 
latitude 
of ? . 

Halley’s er- 
ror, 

DE LA LAN Dt’s 
error, 

in long. 

in lat. 

in long. 

in lat. 

1781 
Sept. 13 
22 

oa. 1 
4 

• / // 
i 38 6 

1 43 2 4 
1 49 46 
1 52 11 

s » 0 / // 

6 18 39 15 

6 29 38 48 

7 10 36 42 
7 14 l 5 ! 7 

0 in 

3 28 12 N 

3 3 9 

3 23 48 S 

o 33 3 

// 

+ 11 

+ 17 
+ 16 

T 12 

n 

+ 3 
+ 1 

- 7 

- 4 

11 

+39 

+44 

1/ 

+ 3 
— 2 

1784 
Sept. 20 
25 

oa. 2 

i 4 

21 

0 37 17 
0 39 57 
0 44 49 

0 54 7 

1 0 42 

6 9 40 27 

6 15 52 59 

6 24 35 34 

7 9 3 ° 4 C 

7 18 13 11 

i 6 15 N 

a 57 5 o 
3 44 21 
0 16 41 
313 s 

+ 4 1 

+ 36 
4- 10 
+ 17 

+ 1 5 

+ 3 
4- 6 
+ 1 
+ 1 

+ 17 
4- 18 

+ 12 
+ 3 

1786 
Aug. 19 

2C 

21 

2$ 

2C 

2 25 57 
>2 26 1^ 
2 26 32 
2 28 3C 
) 2 28 4} 

6 4 45 54 
6 5 5 6 11 

6 7 6 42 

>6 15 7 sc 

'6 16 27 31 

0 23 7 N 

o 19 40 
D it) 20 
0 8 46 S 

0 12 32 

- 5 

- l l 

~ l 3 

— 0 

— 22 

- 3 

- 9 

- 5 

- 2 

- 4 

+ 17 

+ 2 3 

— 12 

+ 2 


The angle at the planet or the commutation — P 13 not 
dire&ly to be taken out of the table. The difference between 
the obferved geocentric longitude of the planet and the geo- 
centric longitude of the fun, calculated from M. Mayek’s folar 
tables, is the angle at the earth, or the elongation - T. From 
this elongation, which is to be depended upon to very few 
feconds, and from the planet’s and the earth’s diflances from 
the fun, according to the tables, the commutation is calcu- 
lated, and the geocentric longitude is reduced to the Heliocen- 
tric longitude. The angles P, T, and S, at the fun, thus 

found, are likewife ufed to calculate the heliocentric latitude. 

According 

7 


en the Planets Venus and Mars . 2 3 

According to the different dimenfions, given to the orbit of 
the planet in the different tables, the radius vector at a given 
time will alfo be fomewhat different. Thefe differences in the 
tables of Dr. Halley and M. de la Lande are but fmall: 
thus, 17S4, September 20, at o h. 37' if' mean time, the 
obferved and apparent geocentric longitude of Venus 6 s. 9® 
54^, the aberration and nutation + 33", the corre&ed 
and true geocentric longitude 6 s. 9 0 46' 27", the fun’s geo- 
centric longitude 5 s. 28° 5' 5 1" ; hence the elongation T = 
os. ii° 34' 3 ^'- ^ now the logarithm of the radius vector 

SP is taken out of Dr. Halley’s tables =4.858251, then 

f] n§ p — and P=i6° if 52"; but if the logarithm 

SP 

SP is taken out of the tables of M. de la Lande = 4,858 1 68, 
the angle P will be found =i'6° I2 / the difference is 12". 
This uncertainty in the commutation, and confequently in the 
heliocentric longitude, would have been {till greater if the 
calculations had been made only from the tables, or from the 
planet’s geocentric longitude by the tables ; thus this angle P 
is, according to Dr. Halley, = 16 0 io' 52" ; and from the 
tables of M. de la Lande :=:i6° io' 13". 



■t 


Mean 


24- 


Pnfejfor Bugge’s Agronomical Observations 


r j 

Mean time at 
Copenhagen. 

Heliocentric 
ongitude ot 
$ in the 
ecliptic. 

Heliocen- 
ric latitude 

of ? • I 

Halley’s er- 
ror, 

JE LA LAN DE*S 
error, 

n long. 1 

in lat. 

in long I 

in lat. 

1 78 1 
Sept. 13 
22 

pa. 1 
4 

/ // 
38 6 

43 24 
49 46 
52 11 

s. 0 t // 

7 28 40 26 

8 12 59 47 
3 27 15 26 

9 1 59 21 

0 / H 1 

o 56 13 N 
0 6 4 

0 44 6 S 

1 0 28 

// 

+ 21 

+ 7 ° 

+ 4 1 1 
— 20 j 

// 

+ 5 
+ 2 

-13 

- b 

// I 
+ 6 3 
+ >3 

// 

- b 

— 6 > 

+ 28 
+ l 
+ 74 
+ 33 

1 +55 

+ 34 
+ 7 
+ l 3 
+ 1 
— 2 

+ 106 1 
+ 43 

+27 

4- 7 

1784 

jSept.20 

2 5 

pa. 2 
14 
21 

0 37 17 
0 39 57 
0 44 49 

0 54 7 

1 0 42 

6 25 51 19 

7 3 5 2 40 

7 *5 6 3 2 

8 14 !3 57 
8 15 21 4 ^ 

2 23 46 N 
2 13 7 

1 40 46 
0 36 58 
0 2 17 s 

1786 
j Aug. 19 

2C 

21 

1 ‘ 2C 

2 25 57 

2 26 14 
2 26 3: 
2 28 3C 
)12 ,2.8 4’ 

8 4 12 41 

1-8 5 47 3 : 
18 7 23 xc 

d 8 18 30 2. 
7 8 20 5 i( 

o 37 6 15 

0 31 22 

30 25 55 
0 13 17 s 

D l8 52 

+ 2 5 
+ 5 2 
+ 68 

1+ 10S 
1 + 35 

- 4 
-*5 

- b 

n 

5 

- 6 

+ 69 

+ 89 

-16 

+ 3 


Let the difference between two heliocentric longitudes, one 
before and the other after the paflage through the node be 
—a. the northern heliocentric latitude =b, and the fouthem 
= /3; let the arc of the ecliptic from the node to the longi- 
tude, anfwering to the fouthem latitude, be - x , tnen tang. 
fin, a , tang. 8 By this formula the diftance from 

every longitude with a fouthem latitude to the node may b 
found ; and hence the heliocentric longitude of the noee. 


Obfervations 


on the Planets Venus and Mars. 


25 


Obfervations compared. 

Heliocentric 
longitude of 

CS $ . 

Reduced to 

1786. 

1781 

September 13 — October 1 
September 13 — October 4 
September 22 — OCtober 1 
September 22 ■ — October 4 

s * 0 / // 

8 14 42 42 
8 14 42 23 
3 14 42 29 
8 14 42 12 

s • . . .. 

Mean 

8 14 42 24 

8 14 44 53 

1784 

October 21 — September 20 
October 21 — September 25 
OCtober 21 — October 2 

October 21 — OCtober 4 

Mean 

8 14 43 38 

8 14 43 40 
8 14 43 42 
8 14 43 3 ° 

8 H 43 3 8 

8 14 44 34 

1786 

Auguft 19 — Augii ft 29 

Auguft 19 — Auguft 28 

Augnft 20 — Auguft 29 

Auguft 20 — Auguft 28 

Auguft 21 — Auguft 29 

Auguft 21 — Auguft 28 

Mean 

8 14 45 3 
8 14 44 28 
8 14 44 16 
8 14 44 0 
8 14 44 2 7 
8 14 44 3 6 

8 14 44 28 

8 14 44 28 


Hence the heliocentric longitude of the defending node of 
the planet Venus was , 1786, Augujl 25, at B h. 39 s "j 
8 s. 1 4 0 4.4' 38". I think that this place of the node is to 
be depended upon to 10 or 15 feconds. According to the 
tables of M. Cassini, the longitude of the node 8 s. 14 
48' 31", the difference, or the error, - f S 3 * According 
to the tables of Dr. Habley 8 s. 14 0 42' 39", the difference. 
4. \' 5p // . From the tables of M. de la Lande e> s. 14 
45' 15", the difference only — 3 ~l" ' 

V41,. LXXX. E 


In 


2 6 Profejfor Bugge’s Agronomical Obfervations 

In order to afcertain the annual motion of the node, this 
obfervation is to be compared with the obfervations ot other 
aftronomers. The numbers in the column A are found by 
fetting out from my own obfervations 1786. In the column 
B, the obfervation of M. de la Lande 1769 is taken as the 
fijft ; the feries C is begun with the determination of M. 
Horrox 1639; and in the feries D, M. Cassini’s obfervation 

1698 is taken as the bafis. 


The Aftrono- 
mer. 

The time of 
obfervation. 

Heliocentric 
longitude of 

Q ? • 

Annual motion of & $ . . 

A. 

B. 

C. j 

D. 

Horrox 
Cassini 
Cassini 
Cassini 
de la Caille 
de la Caille 
, de la Lande 
Bugge 

. 

1 639^ Dec. 4 
1698, Sept. 4 
1705, June 1 1 

173L A P ril 7 
1746, Dec. 21 
1761, June 5 
1769, June 3 
1786, Aug. 25 

s * 0 ii > 

2 13 27 50 
2 14 1 45 

2 14 2 52 

2 14 J 7 2 

2 14 23 10 
2 14 3 1 3 ° 

2 14 36 20 
2 14 44 3 8 

Mean 

// 

3 1 >3 
29,2 

3°>9 

3 °’° 

3 2 * 1 

3 1 * 2 

28,1 

// 

3 j »6 

29.2 

3 L 3 

30.2 

34>3 

// 

3 6 »5 

3 L 9 

3 2 >7 

3L0 

3 L 3 
3 j >6 
3 L 3 

// 

24,9 

26,8 

27,3 

29,2 

29,2 

, 3°>4 

3 I »3 

3 2 ’3 

2 7»5 


If the mean be taken of thofe four means, the annual 
motion of Venus's node will be 30 ,37", or very near 31", 
adopted in the tables of Dr. Halley and M. de la Lande. 


11 . The greatefi inclination of the orbit of Venus to the ecliptic. 

In the firft place, I fhall put down the obferved geo- 
centric longitudes and latitudes, corrected for aberration and 

nutation. 


Mean 


on the Planets Venus and Mars . 2*7 


Mean time at Co- 
penhagen. 

Geocentric 
longitude 
of $ . 

Geocentric 
latitude 
of ? . 

Halley’s 

error, 

DE LA LANDE’S 

error, 

n long. 

in lat. 

n long. 

in lat. 

1781, July 20 

24 

30 

3 1 

Aug. 1 

A 

1 

h* / n 

0 1 40 

1 5 45 

1 1 1 18 
1129 
1 12 58 
1 15 21 

s * 0 / // 

4 11 10 49 
4 16 5 52 

4 23 28 41 
4 24 42 29 
4 2 S 55 54 
4 29 37 *3 

0 / // 

1 24 46 N 
1 27 21 

1 29 21 
1 29 36 
1 29 21 
1 29 4 

// 

+ 3 ° 
4 21 
+ 29 

+ 3 2 
4- 18 

4 20 

// 

+ 5 
4 5 

4 - 9 

+ 12 

+ 3 
+ 7 

// 

-f 69 

// 

+ io 

1782, July 13 
Nov. 5 

21 9 19 

22 50 43 

2 10 54 1 7 

6 29 46 25 

2 12 22 S 
1 21 1 1 N 

+ 53 
4 40 

4 2 

JL 0 

‘ 0 

+47 

4 - 6 S 

+ 3 
4 4 

1783, Sept. 19 

20 

26 

Oft. 2 

2 4 37 

222 

1 43 5 8 

1 22 55 

7 3 52 2 9 

7 4 >5 J 1 
7 5 55 9 

1 6 20 38 

6 3 1 S 

0 10 26 

6 50 19 

7 20 29 

-ns 

— 122 
— 190 

-i 3 ° 

1 

+39 

+49 

+55 

+58 

+ 6 

+ 3 
+ *5 
+ 3 

-58 

-24 

+24 

+44 

1784, May 18 
Sept. 8 
20 

25 

22 29 58 
O 30 I I 
O 37 17 
0 39 57 

i 7 1 56 

5 24 45 1 1 

6 9 40 27 

6 15 52 59 

1 28 35 s 
I 20 2 N 

1 6 15 
0 57 50 

+ 57 
+ 27 
+ 41 
+ 15 

+ 44 
+ 77 

+ 5 

4 - 12 

1785 J ul y 2 9 

Nov. 27 

20 53 21 

21 29 57 

2 22 5 27 

7 9 3 ° 4 ° 

3 53 17 s 
1 37 43 n 

— 40 

- 5 

+ 13 

+ 4 

~!3 
4 26 

+ 19 
- 2 

1786, June 19 

24 

29 

July 1 
14 

1 43 7 
I 49 2C 

i 55 7 

1 57 17 

2 9 7 

3 21 39 32 

3 27 44 4 l 

4 3 47 4 2 

4 6 13 9 

4 21 54 24 

1 30 40 N 
1 35 5 2 

1 38 54 

1 39 45 

■i 37 40 

+ 12 

+ 53 
+ 3 

4- 9 
- 6 

4 12 
+ 19 

+ 5 

+ 7 
4- 10 

+ 43 

-f 8 

1788, May 6 

7 

9 

3 1 2 4 

3 2 !/ 
3 4 4 

•3 0 23 44 
3 1 28 48 

13 3 38 13 

.2 43 15 N 
2 44 22 
2 46 26 



4- 20 
+ 27 
~T 39 

4 22 , 
4 17 
4 1 4 


The angle at the planet is found in the manner before menti- 
oned. The following table contains the heliocentric longitudes 
and latitudes to the moments of mean time in the foregoing 
table. The heliocentric place of the node is afcertained with 
a tolerable degree of accuracy ; hence the arc of the ecliptic 

E % from 


2 8 Profejfor Bugge’s Agronomical Obfcr vat ions 

from the node to the circle of latitude, palling through the 
planet, is given = d ; the inclination of the orbit to the 
ecliptic -y is to be calculated by this formula, cot. y = 

iin. dx fin. lat. 

- • 

tang. lat. hel. 



Heliocentric 
longitude of 
$ in the 
ecliptic. 

Heliocen- 
tric latitude 
of ? . 

Halley's 

error, 

DE LA LaNDE’s 
error, 

Inclination 
of % *s 
orbit. 

in 

long. 

in lat. 

in long. 

m lat. 


s. 

0 / 

// 

0 

/ // 


// 

// 




0 

/ // 

1781, July 20 

5 

0 0 

53 

3 

16 . 55 N 

+ 

18 

412 




3 

2 3 3 2 

24 

5 

6 30 

59 

3 

2 I 27 

4 

7 

+ 7 


// 

// 

3 

2 3 3 ‘ 

3 ° 

5 

l6 15 

59 

3 

23 36 

4 

12 

4-21 

4 - 1*5 

4-21 

3 

23 41 

3 1 

5 

1 7 53 

28 

3 

23 30 

4 

16 

+29 




3 

23 49 

Aug. 1 

5 

19 30 

3 1 

3 

22 43 

4 

3 

4 - 7 




3 

23 27 

4 

5 

24 22 

35 

3 

20 41 

4 

4 

4 - *5 




3 

2 3 35 

1782, July 13 

0 

4 2 

0 ^ 

J/ 

3 

11 57 S 

1 16 

4 - 4 




3 

23 26 

Nov. 5 

6 

9 46 

4 

3 

4 18 N 

4 - 

40 

+ 5 




3 

2j =7 

1783, Sept. 19 

1 1 

6 41 

2 1 

3 

21 45 s 

— 

97 

+23 

— 

>«3 

+ 23 

3 

23 44 

20 

1 1 

8 16 

1 1 

3 

22 3 1 

— 

105 

4*27 




3 

23 48 

26 

1 1 

*7 45 

5 

3 

23 3 ° 

— 

*75 

4-28 




3 

2 3 47 

Oct. 2 

1 1 

27 16 

44 

3 

18 56 

— 

1 1 7 

+ 31 

• 

! 95 

+ 3 ° 

3 

2 3 49 

1784, May 1 8 

0 

5 34 53 

3 

IO 14 s 

4 

7 1 

+ 13 

— 

1 

4 11 

3 

23 34 

Sept. 8 

6 

6 30 

1 1 

3 

8 56 N 

4 - 

18 

4 - 7 




3 

23 27 

20 

6 

2 5 5 1 

r 9 

2 

23 46 

4 - 

28 

+ 3 ° 

f 

“T 

1 16 

427 

:> 

2 3 5 8 

25 

7 

3 52 

40 

2 

13 7 

4- 

1 

4 - 7 




'i 

2 3 33 

1785, July 29 

1 1 

15 44 

9 

-> 

23 30 s 

— 

68 

4-12 

— 

*54 

4 12 


23 32 

Nov. 27 

6 

0 5 ° 45 

3 

15 22 N 

4- 

1 

4 2 

4 

99 

— 2 

5 

23 22 

1 78O, June 19 

4 

25 53 

12 

3 

12 43 N 

4- 

1 

4-26 




3 

2 3 4 i 

24 

5 

4 2 

2 

3 

20 31 

4 

44 

4-43 




3 

24 0 

29 

5 

12 8 

55 

0 

23 18 

— 

5 

4-u 




3 

2 3 3 ° 

July 1 

5 

15 2.3 5 s 

3 

2 3 33 

4- 

1 

4* *4 

4 109 

4 14 

3 

2 3 35 

M 

6 

6 28 

2 

3 

9 10 

— 

8 

4-i8 




3 

23 3 8 

1788, May 6 

5 

16 58 

34 

3 23 37 N 




4 

20 

4 20 

0 

23 46 

7 

5 

18 36 

3 

3 

23 1 2 




4 

27 

42i 

0 

2 3 28 

9 

5 

21 50 5t 

3 

22 4 




4 

39 

4-19 

3 

2 3 3 8 

' 










Mean 

3 

2 3 37>7 


i 


The 


on the Planets Venus and Mars. 29 

The heliocentric latitudes obferved 1781 July 30, 1783 

September 26, 1785 July 29, 1786 July 1, 1788 May 6, 

are very near the greateft latitude ; the mean of the inclina- 
tions found on thefe days is 3 0 23' 40, "2, and very near the 
mean of all the obfervations f 23' 37", 7. The inclina- 
tion, or the greateft heliocentric latitude, may alio be found 
bv interpolation of the maximum amongft the obferved helio- 
centric latitudes. This maximum is found 1781=5° 23' 39" 


1783 = 


o° 2 2 
0 


' A \ " 

4 l 5 


i j86 


o' 

D 


2 3 ' 


the mean of thofe 


three maximums 3 0 23' 38", 6, which inclination may be 
depended upon to 1 or 2 feconds The inclination of the orbit 
of Venus has been fuppofed in the tables of M. Cassini, Dr. 
Halley, and M. de la Lande, = 3 0 23' 20", and the error 
of the tables + 1 8 ,6. 


III. The heliocentric longitude and motion of the nodes of Mars. 

In a Paper printed in the Memoirs of the Royal Academy 
of Sciences at Stockholm, I have determined the heliocentric 
longitude of Mars's afcendmg node— \ s. \f 54/ 2 4/', 2, m the 
year 1783, December 7, 20 h. 23' 39", mean time at Copen- 
hagen: the error of M. Cassini s tables — io / 35 » hb. 
Halley’s tables — 23 / 27 ^ of M. de i.a Landes tables 
- 4/ on". I refer the reader to that Paper (Kongliga Svenlka 
Vetenlkaps Academiens nya Handlingar, Tom. "V I. for the year 
1785, p.285 — 290.). The annual motion of Mars’s node 
may be found by comparing the following obfervations of the 
longitude of the node. In the column A the numbers are 
going upwards from the obfervation 17^3 ’ ■ the column I> 
the numbers are going downwards from the obfervation 1595- 


The 


3 ° 


Profefor Bugge’s Agronomical Obfervations 


The name of the 
aftronomer. 

Time of obfer- 
vation. 

Heliocentric lon- 
gitude of & £ . 

Annual motion. 

A. 

B. 

Tycho Brahe 
Cassini 
Cassini 
de la Caili.e 
de la Caille 

\ 

Maskelyne 

Bugge 

1 595, Oct. 28 
1700, May 6 
1721, Nov. 13 
1747, May 14 

1753 * Nov - 4 
1778, April 1 7 

1783, Dec. 7 

8 * 0 / // 

1 16 24 33 

1 l l 13 43 
1 17 29 49 

1 17 37 11 

1 17 42 5 

1 17 51 40 
1 17 54 24 

Mean 

// 

28.7 
28,9 

23.8 

2 7>5 

24.6 

28,5 

// 

29.4 

3 L 3 

28,9 

29.6 

2 <I ,3 

28.7 

27,0 | 29,5 


The mean of the two feries A and B will give the mojl 
probable annual motion of Mars's node 28 ',2. In the tables or 
M. Cassini the annual motion is 34/ , in the tables ot Dr. 
Halley 38", and in the tables of M. de la Lande 40". 


IV. The inclination of the orbit of the planet Mars. 


Mean time at Copen- 
hagen. 

Geocentric lon- 
gitude of $ . 

0 

Geocentric 
latitude of 

i . 

£rror of the tables of 
M. de la Lande, 

in long, j 

in lat. 


/ // 

s • 0 / // 

0 

r // 

// 

it 

1788, Jan. 9 

11 57 7 

3 16 27 7 

4 

5 25 n 

+ 17 

4 - 1 

10 

II 51 28 

3 16 3 35 

4 

6 io 

+ 19 

+ 7 

1 1 

11 45 5 ° 

3 i 5 40 15 

4 

6 44 

+23 

+ 10 

26 

lO 24 5O 

3 i° 43 39 

4 

3 59 

+ 45 

+ l 9 

Feb. 14 

8 58 52 

3 8 13 29 

3 

39 35 

— 8 

+ 8 

Mar. 9 

7 37 35 

3 11 13 55 

3 

1 1 3 

- 7 

- 4 

12 

7 29 7 

3 n 59 16 

2 

5 6 5 2 

+ 2 

+ 7 

J 3 

7 26 19 

3 12 15 21 

2 

55 24 

+ 2 

+ 9 

14 

7 23 35 

3 12 31 44 

n 

53 5 6 

+ 3 

+ 8 

16 

7 18 10 

3 i 3 5 S 8 

2 

50 56 

— 18 

+ 7 

April 6 

6 27 49 

3 20 29 42 


22 46,7 

- J 7 

+ 8 


The geocentric longitudes of Mars are corrected for aberra- 
tion and nutation, and compared with M. de la Lande’s 

n ewe ft 



on the Planets Venus and Mars. 


3 l 


neweft tables, which after the laft improvements commonly 
^ive the true place of Mars within the fourth part of a minute. 
The error in longitude + iy" fignifies that the longitude in 
the tables is 1 7" too fmall ; and that thofe if' are to be added 
to the calculated longitude, in order to make it agree with the 
obferved longitude. 


Mean time at 
Copenhagen. 

Heliocentric 
longitude of 

$ . 

Heliocentric 
latitude of S • 

1788 
Mar. 9 
12 

J 3 

14 

16 

0 / t/ 

7 37 35 
7 29 7 
7 26 19 

7 23 35 
7 18 19 

0 / // 

4 15 12 28 
4 16 31 42 
4 16 58 8 

4 17 24 28 
4 18 16 5c 

i 50 49,1 N 

1 5 ° 53>5 
1 50 56,0 

1 S° 57,7 
1 50 56,7 


Error of the tables of 

M. de la Lande, 

in long. 

in lat. 

// 

// 

- 7 

- 3 

+ 2 

- 4>5 

+ 2 

- 3 

+ 3 

- H3 

- 4 

- 2,3 


Inclination 
of the orbit 
of $ . 


// 


1 5° 5 6 
i co c6 

t So 56,4 
1 So 57,7 
1 5° 56,7 f 


The inclination of Mars is taken in the tables of M. Cassini 
* c 5 q/ 54 // > in tables M. Lande and Dr. 

Halley i° 5 1 ' o". 

I (hall conclude this Paper with the oppofition of Mars 
according to the foregoing obfervations. The oppofition of 
Mars to the fun happened 1788, January 7, at 8h. 19 32 

true time ; the apparent geocentric longitude of Mars at that mo- 
ment = 3 s. 17 0 if 8 7/ , and the geocentric latitude = 4 4 3 
Saturn was in oppofition to the fun, Auguft 29, 20 h. 51 11 
true time; the apparent longitude ^ — 1 1 s. 7 ° 3 1 34 5 anc ^ 
latitude i° 33^ S. The new planet was in oppofition to 
the fun January 18, oh. 28' 33^ true time, the longitude = 
3 s. 28° io' f\ and latitude o° 34/ 35" N. 




[ 3 2 3 


■ / 

111 An Account of feme luminous Arches. In a Letter from 
'Mr. William Hey, F. K. S. to the Rev. Jofeph Prieftley, 

LL . D. F. R. S. 


Read December 14, 1786. 

REV. AND DEAR SIR, Leeds, Dec. 31, 1783. 

B EFORE I deferibe the luminous arches which I have 
fee a fmee the commencement of this year, I (hall give 
vou a fhort account of two, which I faw iome years ago, 
though I made no obfervations upon them which could at all 

illuftrate their origin. 

While 1 was at Buxton, in March 1774* 1 was called out 
bv feme gentlemen, about half pad eight in the morning, to 
fee a luminous arch, which appeared very beautiful in the 
atmofphere. Being then indifpofed, I durlt not flay out of 
doors any confiderable time to examine it, and only made the 
following obfervations refpe&ing it. Its colour was white, 
inclining to yellow; its breadth in the crown apparently equal 
to that of the rainbow. As it approached the horizon, each 
leg of the arch became gradually broader. It was Rational y 
while 1 viewed it, and free from any fenfible corufcations. Its 
direction feemed to be from about the N.E. to the S.W. at 
lead its eaftern leg was inclined to the north, and its weftern 
to the fouth. Its crown, or mod elevated part, was not far 
from the zenith. The evening was clear, and the ftars 


A 


Mr. Key's Account, &c. 33 

appeared bright. It continued about half an hour after it was 
firft obferved by the company. 

In October 1775, I law a funilar arch at Leeds, of the 
fame colour, breadth, and pofition. It began to difappear in 
five or fix minutes after I had difcovered it, without changing 
its fituation. The manner in which it vanilhed was quite irre- 
gular ; large patches in different parts, and of different dimen- 
fions, ceafing to be luminous, till the whole had disappeared. 
The evening was rather cloudy. I made no obfervation on the 
Hate of the wind during the appearance of either of theie 
arches. 

Having read Mr. Cavallo’s Paper in the Philofophical 
Tran faff ions *, containing a defcription of a fimilar phaeno- 
menon, with fome remarks upon its nature, I determined to 
pay a greater attention to this meteor, if I Ihould ever happen 
to fee it again. During the laft fpring it appeared fo often, 
and with fuch a variety of circumftances, that I had an 
opportunity both of gratifying my curiofity, and fixing my 
judgement concerning it. 

As I was travelling in the evening of the 21ft of laft March, 
betwixt eight and nine o’clock, I obferved fomething like a 
bright cloud in the eaftern part of the hemifphere ; and fuf- 
pefting that it might be of the kind above defended, I looked 
through the glafs in the back part of the chaife in which I was 
riding, and faw a fimilar appearance in the oppofite part of the 
heavens. 1 immediately ordered the driver to flop, that 1 
might make as accurate an obfervation as my fituation would 
admit. I faw that the luminous bodies, which appeared in 
the eaftern and weftern parts of the horizon, were gonnedled 
by an arch of a fainter light ; and recollefling that the beft 

* Voh LXXI. p. 329. 

F 


Vol. LXXX. 


method 


^ a Mr. Hey’s Account of 

method of afcertaining the courfe and dimenfions of this arch 
would be to obferve fome of the principal conflellations before 
which it paffed, I made fuch remarks as I was able ; and after- 
wards, by the afiiftance of a celeftial globe, while the circum- 
flances were frelh in my memory, I drew up the following 
account of this, and fome other arches which I afterwards 
faw\ 

The arch which I faw fir ft arofe at E. by N. afcending 
through the conftellation Bootes, and having, with refpecl to 
the breadth of the arch, Ar&urus in its center. Its fou them 
edge paffed a little to the north of Caftor in Gemini, and de- 
fended clofe to the ftar Bellatrix in the left fhoulder of Orion. 
It reached the horizon in the W.S.W. point. In this courle it 
paffed about 12 0 to the fouth of the zenith. Its breadth w'as, 
according to the beft judgement I could form, about 9 or 10 
degrees. It remained vilible about 10 or 12 minutes after I 
had firffc difcovered it, and then vanifhed gradually and irre- 
gularly. I obferved no corufcations, nor any motion in this 
arch. 

I had fcarcely travelled a mile farther, when another, and 
ftili more beautiful, arch made its appearance. It arcle a 
point or two nearer the N.E. than the former had done. Its 
fouthern edge paffed up a little to the north of the tail of the 
great Bear, which was then in a vertical pofition. Its northern 
edge appeared at firft a little to the fouth of the polar (far ; 
but, during the continuance of the phenomenon, it gradually 
receded about 10 degrees to the fouth. The arch defended 
about the W.N.W. ; but neither the eaftern nor wedern ex- 
tremities reached the horizon ; each of them ending in a point 
gradually formed a little above the horizon. This arch might 
be about 10 or iz degrees at its vertex. It continued vilible 
1 for 


fome luminous Arches* 3 5 

i 

for half an hour ; and although I could not difcover any coruf- 
cations, or quick motion, In any part, yet the different por- 
tions of it were perpetually varying in the denfity of their 
light, and the whole arch, or at leaft its vertex, made a flow 
and equable motion towards the fouth. Where the light was 
the mod denfe, the fmaller ftars were rendered invifibl^ by the 
arch, but ftars of the fecond magnitude were not totally 
eclipfed by it. This arch difappeared, as the former, by 
patches ; the light gradually becoming lefs intenfe. The 
colour of both thefe arches was white. 

Before the latter arch had intirely difappeared, a fmall one, 
not quite fo broad as the rainbow, arofe from its eaftern leg, 
and afcending in a curvilineal diredtion to the polar ftar, ter- 
minated there. Its light was more faint than that of the 
other two arches. It continued vifible about a quarter of an 
hour. 

When I ufe the terms afcending and defending , I would not 
be underftood to mean, that the appearance of thefe arches 
was progrejfive from eaft to weft : they were all completely 
formed when I firft difcovered them ; even the fmall and im~ 
perfedt arch laft mentioned, which appeared while I was exa- 
mining the larger one, had no progreffive motion. I firft faw 
it complete, though a few minutes before there was nothing 
luminous where it appeared. 

The evening was very fine when I faw thefe beautiful phe- 
nomena ; the ftars were bright, and there was not a cloud to 
be feen except in the horizon. There was a fteady light in 
trie north, without the leaft corufcation, extending from the 
N.B. to N.W. The wind blew from the N.E. 

On the 26th of March, about the fame time in the evening, 
I was entertained with a fimilar appearance, as I was travelling 

F 2 


m 


, Mr. IIey’s Account of j 

in the country. I firft obferved two or three columns of 
aurora borealis (hooting upwards in the north ; and m a fhort 
time after I faw a complete arch, like thofe already defcribed, 
though fomewhat different in its pofition. It arofe between 
the E. and N. and N.E. points, pafled obliquely to the fouth 
below Ardurus, and defcended in the weft through Orion, 
having almoft the fame direction through that conftellation 
'which the equator has. It was the moft luminous in Orion, 
and juft below Ardurus. A fmall black cloud crofl'ed it in the 
eaft, and hid a part of it, equal to the breadth of the cloud, 
from view. Its light was the moft faint about the vertex of 
the arch. Its moft denfe parts were continually varying in the 
mtenfity of their light. The larger ftars were vifible through 
its denfeft parts. It varied its pofition, which 1 could heft ob- 
ferve where it pafi'ed through Orion ; for there it moved not 
lefs than io degrees towards the fouthern part of that confte - 
lation. It continued vifible about half an hour ; and, although 
I paid as ftrid attention to the changes which pafled m it as 
my fituation would admit, yet I obferved nothing which could 
be called a {hooting or quick corufcation. There was a fteady 
northern light all the evening, or at leaft till the arch had 

difappeared. 

The moft grand fpecimen of this phenomenon which 
I have feen appeared on the 1 2th of April, betwixt nine 
and ten in the evening. I had obferved, for above half 
an hour, as 1 was travelling, a light in the weftern part 
of the atmofphere ; but as this lay in the direction of fome 
iron-works then before me, which often {hoot out a flame 
illuminating the air to a confiderable diftance, I did not 
pay much attention to the appearance. But having pafled the 
thundery, and ftill feeing the light before me, I locked through 


fome luminous Arches . 37 

the hind-glafs of the carriage, and law the fame luminous ap- 
pearance in the eaft. This roufed my attention ; and imme- 
diately letting down the glades, I looked out and perceived 
a broad arch of a bright pale yellow, arifing between Arfturus 
and Lyra, about the right leg of Hercules, and paffing confident 
b]y to the fouth ot the zenith, its northern border being 
a little fouth of Pollux, and defending to the horizon near 

Orion, which was then fetting. 

This arch feemed to me to be about 15 degrees in breadth, 
and was of fuch a varied denfity, that it appeared to confift of 
fmall columns of light, which had a fenfible motion. 

I had fcarcely viewed this arch above ten minutes, when I 
faw innumerable bright corulcations, (hooting out at light 
angles from its northern edge, which was concave, and elon- 
gating themfelves more and more till they had nearly reached 
the northern horizon. As they defended, their extremities 
were tipped with an elegant crimfon, fuch as is pioduced by 
the eledlric fpark in an exhaufted tube. After fome time this 
aurora borealis ceafed from fhooting, and formed a range of 
beautiful yellow clouds, extending horizontally about a cju al- 
ter of a circle. - 

The eaftern leg of this arch feemed to me to make an angle 
of about 60 degrees with the horizon \ and when I traced out 
the courfe of the arch upon the celeftial globe, 1 judged that 
the center of it muft have palled about 30 degrees to the fouth 
of the zenith. The crown of the arch appeared convex towards 
the fouth, and concave towards the north. The greateft part 
of the aurora borealis which darted from this arch towards 
the north, as well as the cloudTike and more ftationary aurora , 
were fo denfe, that they hid the ftars from view. The moon 
was eleven days old, and fhone bright during this fcene, but 


^8 Mr. Hey’s Account of 

did not eclipfe the brightnefs of thefe corufcations. The wind 
was at north, or a little inclined to the eaft. 

The laft phenomenon of this kind which I faw was on the 
26th of April. Having gone into my ftudy about a quarter 
before ten in the evening, when the window-fhutters were by 
accident left open, 1 obferved in the W. a luminous appearance, 
of the colour of the mod common aurora borealis . From this mals 
or broad column of light iffued three luminous arches, each of 
which made a different angle with the hoirzon. Fnat neaieit 
to the fouth feemed to arife at right angles with the horizon ; 
while that neared to the north made the fmaneft angle, and 
paffed towards the N.E. through the conffellation Auriga, 
having Capella clofe to its upper edge. 1 he houies adjoining 
to my own prevented me from leeing the termination 01 any 
of thefe arches; and neither the time during which they re- 
mained vifible, nor the obfeurity of the atmofphere, would 
permit me to trace their courfe with more accuracy. I had not 
viewed them many minutes when they were rendered in vifible 
by a general blaze of aurora borectlis , which poiletled the jpace 
juft before occupied by thefe arches. 

As there was nothing peculiar in the appearance of this 
mrora borealis , except that it feemed to proceed from the W. 
where I had firft obferved the large column of light, I attended 
to the effeft which the corufcations had in obfeuring the light 
of the ftars. 1 was foon fatisfied that where the aurora borealis 
was denfe, it in tireiy hid from view the ftars ot the fecond 
magnitude. I obferved this particularly with refpect to the 
ftar 13 in the left (boulder of Auriga. But the corufcations 
were never fo denfe, while I (laid to look at them, as to render 
Capella invifible. The wind was betwixt the IN. and IN.E. 
this evening. 


After 


fome luminous Arches . 29 

After comparing the phenomena above defcribed with each, 
other, and with thofe obferved by Mr. Cavallo, in London, 
March 27, 1781; by Mr. Swinton, at Oxford, Od. 12, 
1766, and April 23, 1764; by Dr. Huxham, at Plymouth, 
Feb. 15 and 16, 1749-50; and by Mr. Sparshal, at Wells 
in Norfolk, Jan. 23, in the fame year*; I cannot entertain a 
doubt, that thefe arches had all the fame origin ; and that they 
ought to be confidered as a fpecies of that kind of meteor 
called aurora borealis . 

As Mr. Cavallo has given fome reafons for diflenting from 
this opinion, with refpect to the arch which he defcribes, I 
fhall take the liberty of communicating my thoughts upon his 
arguments. His words are as follows : 44 This extraordinary 
44 appearance to me feemed quite diftindt from the aurora bo- 
“ realis, for the following reafons ; viz. becaufe it eclipfed the 
44 ftars over which it pafled ; becaufe its light, or rather its 
44 white appearance, was ftationary, and not lambent ; and 
44 becaufe its direction was from eaft to weft.” 

1. Mr. Cavallo certainly miftakes in fuppoftng that the 
ftars are not eclipfed by the aurora borealis. The corufcations 
which I faw on the 12th and 26th of April were more denfe 
than the white arches feen in March. The former ren- 
dered ftars of the fecond magnitude invifible ; but thefe I could 
difcern though the white luminous arches. The aurora ko~ 
realis r feen by Mr. Arderon, at Norwich, Jan. 23, 1750, 
eclipfed ftars of the firft magnitude. 

2. The ftation ary appearance of fome of thefe arches does 
not, I apprehend, invalidate the opinion I have entertained 
concerning their nature. For the more common aurora borealis 
may now and then be obferved to remain ftationary for a time. 

% See Philofophical Tranfa&ions for tkefe feveral, years. 


Mr. Key's Account of | 

That which I faw on the 12th of April, and which appeared 
like a range of bright yellow clouds, continued fixed for a 
confiderable time, though apparently formed by the comoi- 
natioti of fome corufcations, which a little betore had been 
moving with rapidity. Befides, though there were no co- 
rufcations obfervable in the arches which I law in March, 
yet all of them, except the imperfect one, were perpetu .lly 
varying in the intenfity of their light ; a circumftance which 
fometimes takes place in the aurora boreal.*, when little or no 

(hooting motion can be perceived. 

Mr. Swinton obferved in the white arch, ieen by him in 
1764, an appearance which approaches (fill nearer to that of 
the common aurora. “ An internal undulating motion or the 
“ the particles conftituting the luminous matter, w-hich w as 
“ difcernible from the firft to the laft moment of its exij - 
“ ence” And Dr. Huxiiam deferibes an appearance in the 
luminous arch feen by him, Feb. .5, i 7 5 ^ which approaches 
{fill nearer to that of the aurora borealis. “ Near the top ot 
“the arch, feveral very lucid, white, fliort, vibrating co- 
“ lumns were attached to it” at right angles, as appears by 
the annexed drawing, fome of which were tix or feven degrees 
in length. But the appearance of the arch which Haw the 
1 2th of April would,, in my opinion, have precluded or 
removed all doubt in any fpedator with regard to the nature ot 

this phaenomenon. . . , , 

The luminous arches which 1 have feen exhibited a pleafing 

diverfity with refpeft to their motion ; lome of them having 

none other than fuch as refulted from a varying intent icy or 

their livht, or an internal undulation } others moving .wwly 

and equably in all their parts; and others feeming to conlm ot 

united corufcations, or emitting the moft vivid dalhes or co- 


loured light. 


Thp 


Jome luminous Arches • 4 1 

3. The direction of thefe arches from eaft to weft feems to 
me to afford no fufficient objection to our confidering them as a 
fpecies of aurora borealis : for if we fuppofe them to be formed 
by ftreams of eleftric matter, flowing in a meridional direc- 
tion, which are either flopped in the atmofphere, or rendered 
vifible at a certain diftance from the north or fouth ; this 
electric matter muft acquire the form of an arch, the pofition 
of which will be from eaft to weft. This idea, refpedting the 
origin of thefe luminous arches, is naturally fuggefted by Dr. 
Huxham’s defcription above quoted, and other of the preceding 
obfervations. The phenomenon of the 12th of April laft 
almoft forces this idea upon the mind, and demands affent. 

After weighing the preceding oblervations, you will not, I 
hope, think me precipitate, if I venture to give a name to the 
meteor I have been deferibing, and call it the arched aurora 

BOREALIS. 

Some luminous arches of this kind, which I did not fee, 
were obferved by others in the courfe of laft fpring. An ac- 
count of one was publifliedin the Newcaftle Paper, and another' 
was feen at Leeds. 

It is remarkable, that the greateft part of thofe which have 
been publicly noticed appeared near the equinoxes. The poles 
of all the complete arches which I have feen had a we ft era 
variation from the pole of the equator. The arches afeended 
obliquely towards the fouth; and in all the inftances in which 
I obferved the courfe of the wind, it blew from fome point 
between the N. and N.E. That feen by Mr. Swinton, in 
April 1764, was the reverfe of thefe in feveral particulars. 
Its pole was directed to the N.E. ' It afeended obliquely to the 1 
north of the zenith, and was preceded by a wind blowing 
from between the N. and N.W. 

Vol. LXXX, G 


Thefe 


4 2 Mr . Hey’s Account , &c. 

Thefe circumftances were perhaps merely accidental ; though, 
in our prefent date of imperfect knowledge refpefting thefe 
meteors, it may not be amifs to take notice of them. In one 
of the inftances related by Dr. Huxham, the wind was 
N.W. by N. ; in the other it was eaft. 

Before I conclude this account, already I fear too much pro- 
trafted, let me hazard a conje&ure refpeaing the white colour 
and ftationary continuance of fome of thefe arches. Experi- 
ments in elearicity, made with what is called an exbaufted 
receiver, fhew, that the colour and motion of the elearic fpark 
vary in proportion to the rarity of the air in the receiver. The 
more the air is rarified, the more moveable and coloured is the 
elearic aura paffing through it. On the contrary, the colour 
of the fpark approaches to whitenefs, and moves with greater 
difficulty, as the air is admitted. Will this obiervation ferve 
in any meafure to account for the difference in colour and 
motion of thefe elearic arches, for fuch 1 prefume to Call 
them? May we not fuppofe the more coloured and trail - 
fient corufcations of aurora borealis to be made in the rarer 
parts of the atmofphere, while the more white and ftationary 
ones poffefs the denfer parts * ? The whiteft arches which I 
. fa w were the moft fixed; that feen April 12. was the mod 

coloured, and had the moft internal motion. 

I am, &c. 

WILLIAM HEY. 

* The luminous arch feen by Mr. Swinton, Oft. 12, 1766, the edges of 
which were in a vertical pofition, feems clearly to have been formed in the lower 
part of the atmofphere : for, while “ the upper or exterior limb was white and 
“ refplendent, the lower was' obfeure, and fcarcely diftinguifliable uom the 
a clouds,” 


C 43 ] 


IV. Extract cf a Letter from F. J. H. Wollnfton f dated Syd- 
ney College, Cambridge, February 24, 1784) to the Rev, 
Francis Wollafton, LL.B. F, R . S. 


Read December 14, 1786. 

— - 1 

I SEND you an account of a remarkable ftream of light 
which appeared laft night, from about 9 h. 5' to 9 h. 25b 
extending entirely acrofs the hemiiphere from W. to E, It 
role from the horizon, about io c S. of W., near $ and y Ceti; 
thence afcended in a ftraight line, inclining a little S. to 
$ and e Tauri, where it made an angle with its former courfe, 
and proceeded nearly in a vertical circle over /3 Aurigae, 
9 Urfe majoris, by Cor Caroli to Ardturus, fetting in the hori- 
zon about 20° N* of E. The light was fteady, not undulating 
like Aurora ; and as it converged towards the horizon at each 
end, had much the appearance which I conceive the tail of 
a comet mu ft make whofe nucleus is juft in the horizon. 
That was particularly the cafe at the W. end, where it was 
brighteft, growing gradually fainter towards the zenith ; the 
E. part was nearly of the fame brightnefs. The greateft 
breadth of the ft ream in the zenith was about equal to the 
diftance between the Pointers in Urfa major. It difappeared 
gradually. When firft I law it, it did not incline fo much 

G 2 towards 


+ Mr. Wollaston’s Account, &c. 

towards the S. at its W. end as afterwards ; but rofe direaly 
up from $ Ceti to the zenith. I flaould like to know, whether 
this has been feen elfewhere, and in what direction. 1 re- 
narked it, becaufe I never faw a ftream extend io fteadil v acrofs 
the heavens. There was very little of Aurora in any other part 
ofthefky; indeed what would not havebeenobiervedatr.il, 
had it not been for this ftreaiTi* 


\ 


i 



\ - 





£ 45 ] 


V. An Account of a luminous Arch. In a Letter from the Rev, 
Mr. B. Hutchinfon to Sir Jofeph Banks, Bart. P. R. S. 


Read December 14, 1 786. 

c T ^ Kimbokorij Feb. 24? 1 7 

L AST night (Monday 23.) at nine o’clock, a very un- 
common aurora borealis appeared here. When I was 
called clown to fee it, it had formed a perfedt, uniform femi- 
circle, of the apparent breadth of half a yard, reaching like 
the rainbow (which it entirely refembled, only that its colour 

was Ample), from the W.S.W. horizon to that of the E.N.E. 
Some of the brighteft ftars of the Bull only juft could be feen 
through it. The whole hemifphere was without a cloud ; 
calm ; b the wind had gone down at weft ; a flight fro ft, after a 
warm thaw, was taking place; and, what was moft extiaordi- 
nary, there was no other aurora boieans in the neaveus till 
this began to fade away, which then, however, arofe a little, 
due N., but without any ftreamers; the ring had no vibratory 
motion. If this phenomenon Ihould have luckily been ob- 
ferved at London or Greenwich, data may be had to determine 
its height from the earth. 

With this view I ran for my quadrant, and found its zenith 
diftance on the meridian fouth 1 1 degrees. Kimbolton is 63 
miles N.N.W. of London, latitude 52 0 ao'. 

I have the honour to be, &c. 

B. HUTCHINSON, 




[ ] 


VI. Extract of a Letter from J. Franklin, Efq. relative to <t 
luminous Arch . Communicated by Sir Joieph Banks, Bart . 
P. P. 5 . 

• Read December 14, 1786. 

Blockley, Feb. 25, 1786. 

IT CANNOT help giving you a line to let you know, that I 
JL obferved a very odd appearance in the heavens on Monday 
evening iaft, about a quarter before nine o’clock. Happening 
to go out of the houfe, I was very much iurpriled to fee a 
N white light, broader than a rainbow, pals acrols t lie heavens 
from eaft to weft. At firft I thought it might be a lunar rain- 
bow ; but, after fome moments refleftion. 1 knew it could not 
be from its fituation. I now began to obferve its iituajtion and 
form more minutely. It ./as a bright white light, about 
5 degrees wide in the zen ih, and gradually coming to a point 
both ways. The eaftern point terminated between Arfturus 
and the bright ftar m the Knee of Bootes. "I he weftern point 
came nearly to the ftar marked a in the Whale’s mouth. Tne 
iouthcrn fide of the light was about 5 degrees above Caftor, 
palling eaftvvard above Berenice’s hair, and weftward near 
Aldebaran, and through the Hyades. I obferved it till nine 
o’clock. Aldebaran was fouth of it when I firft faw it ; but it 
palled, and got north, before nine o’clock. At five minutes 
paft nine, no. more of it was to be feen. It gradually went 
oft in a few minutes. The iky was very clear from clouds, and 
the ftars fhone bright, 




[ 47 ] 


VII. An Account of feme luminous Arches. In a Letter from 
Edward Pigott, Efe. to Sir Henry C, Englefield, Bart . 

F. R. S. 


HGUGPI perhaps an account of the phenomenon of 


February 23. has been communicated to the Royal So- 
ciety, I neverthelefs flatter myfelf the following may be of 
fome ufe, as the different appearances were obferved with 

accuracy. 

mt 

Being at Kenfington on the above-mentioned date, I faw 5 at 
nine o’clock at night, a very Angular, luminous arch in the 
fky, about 4 degrees in breadth, refembling much a bright 
white cloud, drawn out in great length, or fomething like the 
uncoloured northern lights, without flafhes, but feeminglymf 
a more fubftantial texture ; the ftars appeared very bright 
through it; it probably had already exifted fome time. At 
about 9 h. f I noted its track thus : it was vifible very near 
the horizon in the N.E , paffing, between Arfturus and tj Roods, 
almoft covered the clufter of Coma Berenices, and (2 Gemi- 
norum, then pafled to the fouth of Aidebaran, over the ftars 
g, or 7 T Orionis, where its light was fainter, and difappeared 
a few degrees lower. Though its fir ft appearance was that of 
a beautiful regular arch, I perceived, after a few minutes, its 
6 form 


Read November 12, 1789. 


BEAR SIR, 


April 25, 1789, 



3 Mr. PiGott’s Account of 

form had varied a little, and became rather twilled, fo that 
j 2 n W as fometimes to the north or fouth of id center, without 
being uncovered. At 9 } h. its light was much fainter, broader, 
and more crooked. At 9 h. 40 ' its length was decreafed, ex- 
tending only as far as the Gemini’s feet. I: alio had moved 
to the fouth of the clutter in Berenice, and of /2 n, palling 
through Cancer. Its breadth at this time was conliderably 
increased, perhaps to more than double what it was at firft, 
and its brightnefs much faded. The fouthern fide became 
flaky, having about half a dozen parts hanging down, not 
unlike the tails of Comets, the north lide remaining even ; it 
feemed aporoaching towards its diffolution. The air was re- 
markably clear, with a cold and ftrong wefteriy wind ; flying 
clouds paffing over it intercepted its light, and confequcntly 
the column appeared divided. The north horizon exhibited a 
faint aurora borealis. I imagine, if this phenomenon was 
well obferved in diftant parts, a parallax might be afcertained 
Sufficiently to give us fome idea of its elevation above the fur- 
face 0 f the earth. Among the phenomena of this kind re- 
corded in the Philofophical TranfacTions, there are two refem- 
bHngfo exactly the above, that they deferve the confideration of 

the learned; one was feen in iJ34'5» tbe ot!;Ci ia 1 749 * 

Some years ago I alfo obferved a few others, very iimilar to 

that juft deferibed ; 1 (hall therefore take the liberty of adding 

a fhort account of them. . . 

At Brufiels, March 14 , 1774* at about feven 0 cloc " 1,1 
the evening, the fky being very clear, there appeared an arch 
refembling a bright white fog, about 8 or 9 degrees broa , 

' tolerably well defined ; the brightnefs of the ftars it covered 
•was diminifhed. It role in the eafteru horizon, palkd through 
the conftellations of W, a, 25, n, A over Aldcbanm, and 


fome luminous Arches. 49 

disappeared in the Bull’s back. The mod condenfed part of 
it was towards the middle in n ; Sometimes it aflumed this 
form and Sometimes that of an arch. The phaenome- 

uon laded about three-quarters of an hour, and Seemed not to 
have gone out of the zodiac, though when it disappeared, it 
was more to the South than when 1 fird Saw it. The air was 
cold, but not frofty. Towards midnight an aurora borealis 
was Seen in the north, which appeared Something like the phe- 
nomenon jud mentioned ; I did not fee it. 

March 15, 1774, at about 7I o’clock in the evening, a 
column of light appeared in the north, Something like that of 
yederday ; weather very fine. 

At Louvain, 1775, April 19, ph. 30', at night, after a 
dorm, I Saw a bright white line of light one or two degrees in 
breadth extending from N.N.E. through N. to N.W. almod 
parallel to the horizon, and elevated about 9 degrees. It was 
brighter in the center, and dars of the third and fourth mag- 
nitude which it covered were much diminiflied in brightnefs ; 
it Sometimes rapidly vanilhed and re-appeared, and altogether 
laded near half an hour. 

Wickhill in Gloucederfhire, 1777, Feb. 26, at about 7 h. 
at night, I Saw a faint white trail of light, not unlike a foggy 
column, about 6 or 8 degrees in breadth. It extended from the 
horizon W. by S. to E. by S. pafiing over the dars in Orion’s 
feet, and a very little to the north ot Sirius. It teemed to 
have no motion, or to alter in brightnefs. The air was rather 
foggy, with a few clouds and a little wind. At about 10 
o’clock a dight aurora borealis appeared in the north with 
dreaks, extending Sometimes to the zenith. 


Vo l. LXXX. 


H 


Thefe 


Mr. Pigott’s Account, See. 

^Thefe kinds of lights feem to differ from the common aurora 
borealis in feveral particulars : their light is more condensed ; 
they affume the form of an arch or column, and appear other 
to the north or fouth of the zenith, though I think ofteneft to 

the fouth. 


I remain, See. 


EDW. PIGOTT. 



* \ 


/ 




» 


\ 




[ s* 3 


VTTT Experiments on the Analyfis of the Heavy Infiammable Air. 
By William Auftin, M. D. Fellow of the College of Phyfaam ; 
communicated by Charles Blagden, M. D. Sec. R. S. 


Read December 24, 1789. 


N a Paper read before the Royal Society in the year 17 
JL I fuggefted an idea, that the heavy inflammable air is a com- 
pound of the light inflammable and phlogiffiicated airs. At 
that time I had obferved, that the heavy inflammable an, or at 
Raft fixed air, is formed upon the decompofit.on of nitrous 
ammoniac by heating it in clofe veffels ; and that this an 
affeded by the eledrical Ihock, like other elaftic fluids into 
whofe compofition the light inflammable air enters. The con- 
dition which I then drew from thofe fads feems to e up- 
ported by feveral fubfequent experiments which now a to 
the liberty of laying before the Royal Society. ou 
hereafter be found, that the real conftitution of the heavy 
inflammable air differs from what I conceive to be therefu 
the fads below recited, the fads themfelves may fti 1 ha 
their ufe, as they exhibit feveral properties hitherto unobferve 
of the moft extenfive compound body we know, excepting 

Several elaftic fluids containing the light inflammable air, 
as the hepatic and alkaline airs, being decomposed by he 
eledric fpark, I was induced to try it on the heavy inflamma 


2 


^ 2 Dr. Austin’s Experiments on 

air, as foon ns I fufpecled that it contained the lighter air ns a 
con flit uen t part. Agreeably to my expe&ation, this experi- 
ment immediately detected the light inflammable air ; for fuch 
an expanfion took place as could not arife from any other 
known fubftance. Thus the heavy inflammable air was fome- 
times expanded to twice its original volume ; and yet, upon 
examining the air fo expanded, not a fixth part of the whole 
was found to have undergone a decompofition : for inftance, 
when two meafures and three quarters were expanded to fix, it 
appeared by experiment, that nearly two meafures and a half 
remained in their original ftate. 

After the inflammable air has been expanded to about double 
its original bulk, I do not find that it increafes further by con- 
tinuing the fhocks. Conceiving that the progrefs of the de- 
compofition was impeded by the mixture of the other airs with 
the heavy inflammable, I palled the Ipark through a mixture 
of the heavy inflammable air and of the light inflammable air, 
obtained from diluted vitriolic acid and iron filings ; but the 
expanfion fucceeded nearly as well as when the heavy inflam- 
mable was ele£trified alone. This is an almoft infurmountable 
obftacle to this mode of inveftigation : yet it has fuch advan- 
tages in other refpe&s, the air to be analyfed being unmixed 
with other fubltances, and only in contafl with the glafs and 
quickfilver by which it is confined, that I determined toprofe- 
cute the fubjeft in this manner as well as I could. 

From this partial decompofition of the heavy inflammable air 
we obtain a mixture of the two inflammable airs with phlo- 
gifticated air ; that is, of the heavy inflammable air not de- 
compofed, of the light inflammable air difengaged by the 
fpark, and of phlogifiicated air. How much of this phlogifti- 
cated air pre-exifted in the heavy inflammable air, and how 

much 


the heavy inflammable Air. 53 

much was difengaged during the operation, it is not eafy to 
determine. Neither are we acquainted with any fubftance 
which will feparate the two kinds of inflammable air by com- 
bining with the one and leaving the other : but we know that 
dephlogifticated air will combine, in certain proportions, with 
each of them, either mixed or feparate ; that with one of them 
it forms fixed air, with the other water. Therefore, by in- 
flaming dephlogifticated air with a mixture of thefe two airs, 
and obferving the quantity of dephlogifticated air confumed, 
and the quantity of fixed air produced, we difcover the excefs 
of dephlogifticated air confumed above what is fufficient for 
the production of the fixed air ; and may conclude, that this 
excefs of dephlogifticated air has combined with light inflam- 
mable air. This conclufion is further confirmed by attending 
carefully to the contraction which takes place upon inflaming 
thefe airs, which is much greater in piopoition to the quantity 
of fixed air produced, when a mixture of the two inflammable 
airs is inflamed, than when the heavy inflammable air is burnt 
alone. It is well known, tnat in all experiments of this kind, 
what remains after the combuftion of the aus mixed together 
in due proportion, and after the ieparation of the fixed air, is 
chiefly phlogifticated air. From a confiderable number of ex- 
periments, conduded with great care and attention to all thefe 
circumftances, I have endeavoured to appioximate to tne quan^ 
titles of the phlogifticated and light mflammable airs difen- 
gaged, when a given quantity of the heavy mtlammable an was 
decompoled. But all that can be attained to, is only an ap- 
proximation to truth. The quantity of air decompofed by 
this method is fo fmall, and the feparation of tne different 
parts into which it is refolved is attended with fuch difficulties, 


x r ^ Dr. Austin’s Experiments on 

that an accurate analyfis of the heavy inflammable air can 
never be obtained in this manner. 

I therefore attempted to decompofe the heavy inflammable 
air by means of fulphur, which readily unites with the light 
inflammable air in a condenfed ftate, and with it forms hepatic 
air. Having introduced fome fulphur into a retort, filled with 
heavy inflammable air, and applied a lufficient heat to melt 
and lublime it, I found, that a confiderable quantity of hepatic 
air was formed. After this air was abforbed by water, I could 
not perceive that the remaining air differed from the heavy 
inflammable air before the operation. Sulphur mixed with 
powdered charcoal, upon being heated, yields hepatic air in 
great abundance, almoft the whole of which is ablorbed by 
water. The fmall unabforbed refidue, which does not exceed 
a hundredth part of the bulk of the whole air, appears to be 
phlogifticated air. 

In whatever manner the heavy inflammable air was decom- 
pofed, whether by palling the electrical fpark through it, by 
melting fulphur in it, or by heating fulphur and charcoal toge- 
ther, an appearance conftantly occurred, which feemed to indi- 
cate, that volatile alkali is formed, whenever the heavy inflamma- 
ble air is decompofed. The circumftance is this : a fmall piece 
of paper, flained with any blue vegetable fubftance, is turned 
green byftanding in the air during any of thefe procefies ; and 
this green is changed to red upon the addition of an acid. The 
inflammable air had been very long expofed to water, and had no 
fuch effeCt upon blue vegetable fubftances before the operation. 

I have concluded thefe analytic attempts with feveral 
obfervations on the formation of fixed air from fome fubftances, 
which confift only of the light inflammable, phlogifticated, 
and dephlogifticated airs, and from others, in which thefe three 


airs 


the hedvy inflammable Air. 55 

airs are combined with fuch matters as cannot be lufpecied ot 
having any place in the competition of fixed air. 

I proceed now to a detail of the experiments, upon which 

thefe obfervations are founded. 

Exp. 1. A bent glafs tube, one-third of an inch in diameter,, 
open at both ends, being filled with, and inverted in quicK- 
filver, 2 — meafures of heavy inflammable air were thrown into 
it, and ele&rical Ihocks were paffed through this air till it 

meafured 4!. 

Lime water being then thrown up to it was not rendered in 
the leaf! degree turbid. 

During the operation a thin depofit, of a whitifh or a(h 
colour, appeared upon the infide of the glafs tube and quick-* 
filver. This was a common appearance, for which I can give 

no reafon. 

The meafure, made ufe of in this and in all the following 
experiments, is } of an inch. T he an being thrown into tne 
tube, the length of the column of air was meafured by a , 
moveable fcale thus graduated. Some objedion may be made 
to fo fmall a meafure ; but it is really unavoidable on this occa- 
fion, on account of the great difficulty of decompofing the 
heavy inflammable air in larger quantities. I attempted it 
upon a larger fcale in ajar perforated with brafs rods, inch as 
is ufed for inflaming airs ; but after having worked foi many 
hours, in palling eledncal fhocks through air confined in one 
of thefe jars, it was not expanded more than one quarter of 
its original bulk. A piece of paper, coloured -with a blue vege- 
table fubflance, was turned green by {landing in the an during 
this operation. 

It was a very tedious work to throw airs into the fmall tuoe 

in fuch quantities as could be expreffed in integer numbers of 

the 


Dr. Austin s Experiments on 

the meafure : I have therefore generally been contented to ufe 
fractional numbers, and have been ftudious only to introduce 
fuch quantities of the airs as were convenient for the expe- 
riments. 

The inflammable air ufed in all thefe experiments was ob- 
tained from foliated tartar. I have alfo paflTed eledtric lparks 
through inflammable air from pit- coal, and found that it 
expanded in the fame manner. Dr. Biggin's * has (hewn, that 
5,5 of inflammable air from foliated tartar inflamed with 7,5 of 
dephlogifticated air, form 5 meafures of fixed air. Dr. Priest- 
ley -j- has deduced nearly the fame proportions of the dephlo- 
gifiicated and fixed airs, by combining the dephlogifticated and 
inflammable airs in a condenfed ftate. In the following com- 
buftions of thefe airs, after accounting for the phlogifticated air 
in the refidues, the quantity of fixed air produced feems to be 
equal in bulk to the inflammable air combined ; and the 
dephlogifticated air to be to the fixed air, or to the inflamma- 
ble, in the ratio of 7 to 5 ; or, in other words, when 5 
meafures of fixed air are formed, it appears, that very 
nearly 5 of inflammable air and 7 of dephlogifticated air have 
difappeared. But in burning different airs there will be con- 
ftant variations in the refults, arifing from the very different 
ftates of the heavy inflammable air ; and therefore, in thefe 
observations, I am obliged to follow the proportions which 
took place in my own experiments. 

Exp. 2. Three meafures and one-third of inflammable air were 
expanded to 5I : the difference is 2^. To this air were added 
3 1 meafures of dephlogifticated air, which increafed the column 
of air to 9 meafures. One eledlrical fipark reduced them to 4, 

# Higgins on Acetous Acid, p, 288, 289. 

f Priestley, Vol. VI. p. 27. 

2 


Lime 


the heavy inflammable Air. ty 

Lime water being then thrown up left only three meafures of 
air. A foliation of liver of fulphurdid not reduce it further. The 
remaining air inflamed upon being brought near a candle in the 
open air. 

In order to account for this, it muft be obferved, that, be- 
fore the inflammation, the airs occupied the fpace of 9 mea- 
fures, and were reduced bv combuftion and lime water to 3. 
The contradtion is 6 meafures. Of thefe the meafure of 
fixed air accounts for 2,4, allowing 1 meafure of inflammable 
air and 1,4 of dephlogifticated air to produce 1 meafure of 
fixed air, according to the proportion ftated in the laft page ; 2,4 
meafures, which thus went to form fixed air, being taken from 
6, which is the whole contraction, leave 3,6. If we fuppofe 
this contraction of 3,6 to have arifen from the union of the 
light inflammable and dephlogifticated air, very nearly 2,4 
meafures of the former muft have combined with 1,2 of the 
latter. This explains, with a tolerable degree of exa&nefs, both 
the contraction which takes place, the refidue after combuftion, 
and the quantity of dephlogifticated air combined. For without 
any expanfion, the refidue from 3I meafures of inflammable 
air and 3I of dephlogifticated air, after forming 1 meafure of 
fixed air, would be 4,43, which exceeds the refidue in the ex- 
periment by 1,43. Some dephlogifticated air muft therefore 
be combined, befides what enters into the fixed air : and with 
what other fubftance but the light inflammable air could it 
combine, fo as to occafion a contraction of 3,6 meafures ? 

The dephlogifticated air being in this inftance infufficient to 
fa tu rate the inflammable airs, it could not be afcertained how 
much of the heavy inflammable air was decompofed, and hop. 
much remained in its original ftate. The two following expe- 
riments were therefore made in order to determine, in what 
Vol. LXXX. I proportion 


/ 


^3 Dr. Austin’s Experiments on 

proportion the dephlogifticated sir is Sufficient to Saturate this 
inflammable air, and what quantity of fixed air they produce 
when inflamed. 

Exp. 3. In a large exploding jar I mixed 4 1 meafures of 
heavy inflammable air with 7* of dephlogifticated air. After 
explofion thefe airs meafured Something more than 6£, and were 
reduced by lime water to rather leSs than 2f. In this reti- 
duary air a candle burnt with an increafed flame, as in dephlo- 
gifticated air. 

Thus very nearly 4 meafures of fixed air were produced from 
4! of heavy inflammable air. 

Exp. 4. Into the Small bent tube, which was employed in 
the firft and fecond experiments, I introduced 3$ meafures of 
inflammable air, and 5I of dephlogifticated air. Theie were 
reduced by inflammation to 5}, and by lime water to 2}. 

In this experiment, 3 meafures of fixed air were produced 
from 3! of inflammable air. 

In the third experiment, the quantity of fixed air produced is 
4 meafures very nearly. The refiduary air is rather lets than 
if to 2 2 we add a quantity of inflammable air equal to the bulk 
of fixed air, that is, very nearly 4 meafures, it will amount to 6 f 
full meafure ; and if we further add 5,6, which is the quantity 
of dephlogifticated air necefl'ary to form 4 meafures of fixed air, 
we fhall have 11,93, which is within feven hundredths of a 
meafure of the original quantity of the two airs. 

In the fourth experiment, 3 meafures of fixed air are pro- 
duced, which require 3 of inflammable air, and 4,2 of dephlo- 
gifticated air; thefe, added to the 2j meafures of refiduary air 
amount to 9,53, which is two-tenths of a meafure more than 
the original quantity. 


It 


the heavy inflammable Air . 50 

It appears from thefe obfervations, that the proportion of de- 
phlogifticated and inflammable air, in the conftitution of fixed 
air, above ftated, agrees very nearly with experiment. In one in- 
fiance, the quantity arifing from calculating after this proportion 
exceeds the real quantity by two-tenths of a meafure ; and in the 
other, it falls fhort of it by feven hundredths of a meafure* 

It is evident, that 3I meafures of this inflammable air 
burnt in the fmall tube are capable of forming 3 of fixed air..' 
The fixed air, produced by inflaming the fame airs in the large 
jar, bears rather a greater proportion to the inflammable air 
employed ; for 4! meafures of it produced almoft 4 of fixed 
air. I tried many experiments on thefe airs mixed together in 
different proportions, and only in one in fiance found the pro- 
duct of inflammable air greater in proportion than 4 from 4I ; 
which I therefore conceive to be as much as this air is capa- 
ble of producing, and fufpeft, that a fmall error muft have 
been committed in that inftance, which gave a greater propor- 
tion of fixed air. The | of a meafure which remain, are 
chiefly phlogifticated air, mixed perhaps with a very fmall 
quantity of inflammable air ; as will appear from the refidues 
in fome of the following experiments, which contain about 
that quantity of phlogifticated air more than they could derive 
from the dephlogifticated air. Thus, for inftance, in the 
third experiment, the refiduary air meafures 2f, the quantity 
of dephlogifticated air engaged in forming the fixed air is 5,6, 
which added together make 8,1 ; but the whole dephlogifti- 
cated air amounts only to 7,25 ; the difference 0,85 is nearly 
equal to the phlogifticated air, which I fuppofe to have been 
mixed with the heavy inflammable air. 

Exp. 5. Three meafures of inflammable air were expanded 
to 6J, then 4I of dephlogifticated air were added ; after 

I z inflammation 


60 Z)r. Austin’s Experiments on 

inflammation they meafured 4* ; lime water contracted them 
to 2|. 

In this experiment 2 1 meafures of fixed air were formed, 
which is nearly 0,28 lefs than the inflammable air ufed in this 
experiment is capable of producing. We have therefore only 
0,28 to account for the expanfion ; and we cannot fay, that 
the whole of this was decompofed, as the dephlogifticated air, 
even in this experiment, was not quite fufficient to faturate 
the two kinds of inflammable air ; and therefore a fmall quan- 
tity of heavy inflammable air might remain in the rcfidue in 
its original ftate. 

Exp. 6. A quantity of heavy inflammable air, which mea- 
fured between 3! and 3!, was expanded by about 3C0 tleftrical 
fhocks to 6 \ full meafure. To thefe were added 5J ot de- 
phlogifticated air. After inflammation they mealured 4*, and 
were reduced by lime water to 1^. 

The inflammable air in this experiment was between 35 and 
31 ; we will therefore take 3,29, the arithmetical mean of thofe 
numbers. The quantity of fixed air produced is lefs by 0,36 
than could be produced from the fame airs without electrifying. 

It is probable, that a fmall quantity of the heavy inflam- 
mable air may efcape unaltered in each of thele experiments ; 
the following were therefore made with a ftill greater propor- 
tion of dephlogifticated air, and the refidues were examined 
with more attention. 

All the preceding experiments were made with the fame 
airs ; thefe being exhaufted, a frefh fupply was procured for 
thofe which follow. The purity of this dephlogifticated air 
was fuch, that one meafure of it being mixed with 1 1 ot ni- 
trous air was reduced to 0,2 of a meafure. The inflammable 
air was lefs pure than the former. In the two following 

experiments 


the heavy inflammable Air . 6 s 

experiments 4,44 meafures of fixed air were produced from 
5,58 of the heavy inflammable; the remaining 1,18 mufthave 
been chiefly phlogifticated air. 

Exp. 7. Inflammable air 2| and dephlogifticated air 4,^8 
were inflamed in the fmall tube. They then meafured 4J, and 
were reduced by lime water to 24*. After feveral bubbles of 
nitrous air, the refidue was lefs than 2 by nearly J. 

In this experiment 2,09 meafures of fixed air were produced. 

Exp. 8 . In a large exploding jar, 24- meafures of inflamma- 
ble air, and 4, 17 of dephlogifticated air, were reduced by corn- 
bullion to 4,1 nearly, and then by lime water to 1,75. About 
a meafure of nitrous air being then thrown up, the refiduary 
air meafured 1,5. 

The quantity of fixed air produced in this inftance is 2,35. 

Exp. 9. Inflammable air 24. meafures were expanded by about 
200 eledlrical fhocks to 5 and not quite 4 - more. To the air thus 
expanded, I added as much dephlogifticated air as increafed the 
column of air to 9J ; thus the dephlogifticated air was rather 
more than 4,09. After combuftion, they meafured fully 4 ; 
and, after being expofed to lime-water, rather lefs than 2.. 
Nitrous air occafioned a fmall contraction further. , 

According to the proportion ftated in p. 56. 2-^meafures of this 
inflammable air contain 0,58 of phlogifticated air ; 0,58 added to 
2, which went to form fixed air, amount to 2,58. But the origi- 
nal quantity of inflammable air, viz . exceeds 2,58 by 0,2^. 
What becomes of the 0,25 mealures of inflammable air which, 
thus difappear ? I apprehend they muft have undergone a 
decompofition, and have been expanded to 10 times their ori- 
ginal bulk. 

The dephlogifticated air was ftill further increafed in the 
following experiment. 



; g - 4 Dr. Austin’s Experiments on 

Exp. 10. Three meafures of inflammable air, after 1 50 ele£lrical 
fhocks, became 5,1. To this was added as much dephlogifti- 
cated air as increafed the column of air to 10^.. After inflam- 
mation it meafured about 4,9 ; and was reduced by lime water 
to 2 4 • This refidue was not inflammable. 

The contra&ion upon burning thefe airs was 5,93 ; and the 
quantity of fixed air appears to be 2,1 5. This fixed air requires 
2,15 meafures of inflammable air and3,oi of dephlogifticated air. 
Thefe deducted from the fum of the contraction leave 2,92, above 
what is fufficient to account for the fixed air produced. Sup- 
pofing this contraction to have been occafioned by the union of 
light inflammable and dephlogifticated air, 1,94 of the former 
muft have combined with 0,97 of the latter. It is evident, 
that the quantity of dephlogifticated air ufed in this experi- 
ment is more than fufficient to combine with both kinds of 
inflammable air. 

The fixed air produced in thefe experiments is 0,23 lefs in 
proportion, than'was produced, when the inflammable air was 
not decompofed in the feventh and eighth experiments. It 
appears by calculation, that thefe 0,23 were expanded to about 
ten times their bulk. It is obfervable, that the expanfion in 
this cafe is 2,33 ; and that the quantity of light inflammable 
air which combined with the dephlogifticated air, is only 
I 5 q 7j which is 0,40 lefs. This proves, that it is very difficult, 
if not impoffible, to unite the whole of thefe airs ; and that a 
fmall quantity will remain diffufed in the refidue, unlefs the 
airs be much purer than I have been able to procure them ; yet 
it is not probable, that fo large a proportion of light inflam- 
mable air as 0,40 Ihould efcape combuftion, over and above 
what efcapes in fimilar circumftances, when no light in- 
flammable air is prefent. The addition of light inflammable 


the heavy inflammable Air . 

air to a mixture of the other airs would rather contribute to 
render the combuftion more general, and the relid lie confe- 
quently lefs ; for in all combuftion s, the union of the inflamma- 
ble and dephlogifticated airs is more complete, as the proportion 
of phlogifticated air mixed with them is leflened. In gene- 
ral, when air does not burn in fuch circumftances, weprefume^ 
that it is phlogifticated air ; and upon this principle we mu ft 
conclude, that a confiderable part of thofe 0,40 was phlogifti- 
cated air. 

I proceeded to repeat this experiment with a frelh fupply of 
the two airs ; but the tube burfting in the laft explofion, a 
fmaller one was ufed in exp. 12, which however could not 
affeCt the refult of the experiment. 

Exp. 11. Four meafures and a half of inflammable air and 
6f of dephlogifticated were reduced by inflammation to 5! ; 
and by cauftic alkali to 2 and a very, little more. The 
remainder w s not inflammable. 

The produCt of fixed air is 3 f meafures, 

Exp. 12. Two meafures and three quarters of inflammable 
air were expanded to 6 ; then, to reduce the column of air, one 
meafure of dephlogifticated air was added, and the eleCirical 
fpark was palled through the two airs; afterwards 2 meafures 
of dephlogifticated air were added, and the electrical fpark 
again pafled through them; and, laftly, 3,59 meafures of de- 
phlogifticated air were thrown up, and the eleCtrical fpark re- 
peatedly pafled through this mixture of airs. After thefe 
explofions the airs meafured 5!, and after the addition of cauftic 
alkali 3*83. 

The produCt of fixed air is 1,83 ; which is 0,30 lefs in pro- 
portion, than was produced in exp. i x. from the fame inflam- 
mable air not eleCtrified. 


Not- 


64 Sr. Austin’s Experiments on 

Notwithftanding the utmoft attention, we are liable to a 
(mail error in each of thefe experiments ; and there is con- 
fequently a fmall variation in the refults ; but, I think, they 
concur fufficientjy to juftify the following conclusions. 

1. That the heavy inflammable air contains the light in- 
flammable air in great abundance, 

I apprehend this light inflammable air was, before the appli- 
cation of the eledlncal fpark, a conftituent part of the heavy 
inflammable air ; becaufe, if it were contained in the heavier 
-air not as a conftituent part, what fhould hinder its being 

burnt when the heavy inflammable air is burnt ? Can it be 

•/ 

fuppofed, that the heavy inflammable air fhould contain the 
light inflammable air in crrcumftances of combuftion, and that 
the light inflammable air fhould efcape the fire ? And if the 
lighter air be burnt,; the fame quantity of dephlogifti- 
cated air would be neceffary to faturate it before as after its 
being electrified. But it is evident from the preceding expe- 
riments, that much more dephlogifticated air is neceffary to fa- 
turate the air, after it has been expanded by the ele&xical lhock, 
than before. 

2. That no fixed air is formed during the reparation of the 
lighter air from the heavy inflammable air. 

Here it fhould be observed, that if the con flit ution of the 
heavy inflammable air depended on an union of the light in- 
flammable and fixed airs, as florae have fuppofed, we fhould 
certainly difcover the fixed air, when the other part was fepa- 
rated from it. Or, fhould it be conjectured, that the light 
inflammable air is feparated from water fufpended in the heavy 
inflammable air, in that cafe, would not fixed air be formed 
from the other conftituent part of the water uniting with the 


the heavy inflammable Air . 6$ 

heavy inflammable air in confequence of the repeated electrical 
ftiocks ? 

3. That the electrical ftiock feparated a fubftance from the 
heavy inflammable air, which has fome leading characters of an 
alkali. 

When inflammable air is decompofed by fulphur, or when 
hepatic air is made from charcoal and fulphur, we have the 
fame appearance of an alkali. That this is the volatile alkali 
is evident from its evaporation, when hepatic air is made from 
fulphur and charcoal. 

4. That the heavy inflammable air, through which the fpark 
has been repeatedly pafled, when burnt with any proportion of 
dephlogifticated air, does not produce fo much fixed air, as the 
fame quantity of inflammable air not eleCtrified, 

Hence it is evident, that apart of the air is actually decom- 
pofed by the fpark. Hence alfo we may infer, that the decom- 
pofed air is not refolved into light inflammable air and charcoal, 
of which fome chemifts have fuppofed it to confift, becaufe the 
charcoal would combine with dephlogifticated air after its fepa- 
ration from light inflammable air, and we ftiould not have fuch 
a defeCt of fixed air.. 

6. That the refidues, after Inflaming the decompofed air, are 
generally greater than thofe from the air in its natural ftate, or 
than can be accounted for from the mixture of the heavy 
inflammable and dephlogifticated airs. 

This affords a ftrong prefumption, that phlogifticated air is 
extricated from the decompofed heavy inflammable air in a 
feparate ftate, befides what enters into the volatile alkali, 
which is formed at the fame time. If light inflammable air 
only were difengaged during the decompofition, the refidues 
would certainly not be greater after inflammation with a fuffi- 
Vol. LXXX. K ' cleat 


56 Dr. Austin’s Experiments on 

cient quantity of dephlogifticated air; on the contrary, if the 
inflammable air were increafed in proportion in the mixture, 
the combuftion would be more complete, and the refidues 
lefs. 

Having obferved, that fulphur readily combines with light 
inflammable air, if prefented to each other at the inftant that 
the inflammable air is detached from other bodies, before its 
particles have receded from each other, and that hepatic air is 
generally formed in this manner, I introduced fome fulphur 
and heavy inflammable air into a glafs retort, firft filled with, 
and inverted in quickfilver, and applied a fufficient heat to 
melt it. The heat was continued till the fulphur was fublimed. 
The melted fulphur footi acquired a dark reddifh colour ; as 
it fublimed, it became quite black, and every part of the 
retort was covered with a black cruft. On the depending part 
of the retort, where the melted fulphur lodged, and where 
the heat was ftrongeft, there remained a black mark, which 
could not be removed by a much greater heat than that 
by which the fulphur was fublimed. The bulk of the 
air was not materially altered by this operation. A little 
blue paper being thrown up to the air after the opera- 
tion, became green. Water abforbed about one-third of it, and 
acquired a ftrongly hepatic fmell. The inflammable air was 
carefully wafhed, fo as to feparate from it all the hepatic air. 
I then mixed this inflammable air with depblogifticated air, 
and inflamed them, expecting to find a greater quantity of 
phlogifticated air in the refidue, than when the inflammable air 
was burnt, which had not been fubjedted to this procefs. But 
the difference of the refidue does not exceed T X T the quantity 
of air decompofed in this manner, if we may judge from the 
following experiment. 


the heavy inflammable Air, 67 

Experiment. Inflammable air, from which hepatic air had 
been made, and had been feparated by expo fu re to water, 4!, 
and dephlogifticated air 6f, were inflamed in a large exploding 
jar. After the inflammation they meafured 6 ; and after being 
agitated with lime water 2}. This refidue burnt with increafed 

Q 

flame. 

The airs ufed in this experiment were the farrie as thofe in 
the fecond experiment. The quantity of fixed air generated is 
only 0,035 lefs in proportion than was produced in the third 
experiment from the air in its original ftate. 

The refidue is only 0,17 more than it fhould be by calcula- 
tion, allowing the dephlogifticated and inflammable airs to 
enter into fixed air in the proportion of feven to five. 

The remaining heavy inflammable air is therefore very little 
altered as to its quality by this operation, though it is much 
lefs in quantity than can be accounted for from the production 
of hepatic air. For the light inflammable air in the conftitu- 
tion of hepatic air is expanded to the fame degree as in its 
Ample ftate ; and an expanfion might be expeCted, when the 
hepatic air is generated from the heavy inflammable, juft as 
when the lighter air is feparated from the heavy by the electrical 
fhock ; but no expanfion is obferved in this inftance. I there- 
fore fufpeCt, that, when hepatic air is formed in the heavy 
inflammable air, the heavy air is imperfectly decompofed ; that 
only a part of the light inflammable air is combined with ful- 
phur ; and that the remaining parts are precipitated in a ftate 
analogous to charcoal, and blacken the fulphur. Upon apply- 
ing heat to the fulphur thus blackened, I have perceived an 
hepatic fmell. This blackened fulphur is not entirely diffolved, 
like pure fulphur, by being boiled in cauftic alkali, but a black 
powder remains. In one inftance, this black fubftance difap- 

K 2 peared 


£8 Dr. Austin’s Experiments cn 

peared after long boiling in ftrong nitrous acid. More experi- 
ments, than it is in my power to make at prefent, are neceflary 
to determine fully the nature of it. 

The analogy between the heavy inflammable air and char- 
coal is illuftrated by the formation of hepatic air from charcoal 
and fulphur. Thefe fubftances, heated in a fmall glafs retort, 
yield hepatic air in great abundance. The blue vegetable co- 
lour is turned green by expofure to this air. After hepatic air 
had been generated for a long time from the fame materials, 
without admitting any common air into the retort, ninety-nine 
parts in a hundred of the air which came over laft were ab- 
forbed by water. The infallible part appeared to be phlogifti- 
cated air. Thus fulphur and charcoal, heated in a glafs retort,, 
yield hepatic air, phlogifticated air, and volatile alkali, or a 
fubftance very analogous to it. 

As far as I have been able to difeover by experiments, the 
heavy inflammable air and charcoal conflft of the fame ele- 
ments in different proportion. The application of heat to pure 
charcoal confirms this opinion ; for the produdlion of heavy 
inflammable air from charcoal, by mere heat, is conftantly ac- 
companied with a production alfo of phlogifticated air. I ap- 
prehend, that in thefe cafes the charcoal is decompofed and 
refolved into thefe two parts. Whenever charcoal, or any, 
fubftance containing k, is decompofed by heat only, the phlo- 
gifticated and heavy inflammable airs are produced ; and when 
the heat is intenfe, Dr. Higgins has obferved% thatr the air 
produced from thefe fubftances becomes rarer ; as I imagine,, 
in conference of a portion of the heavy inflammable air itfelf 
being refolved by heat into its co-nftituent parts. I would not 
lay much ftrefs on the appearance of phlogifticated air from 

*■ Higgins on Acetous Acid, p, 2.93. 


the 


the heavy inflammable Ain„ ' 69 

the compound forms of vegetable, animal, and bituminous 
iubftances, all of which yield phlogifticated air and volatile 
alkali in great abundance ; yet when the more fimple modifica- 
tions of the heavy inflammable air, as charcoal, vinegar, and, 
if Dr. Priestley is not miftaken, fixed air, give out phlo- 
gifiicated air, when decompofed in clofe veffels, 1 cannot but 
infer, that phlogifticated air is an effential part of that peculiar 
fubftance which exifts in all thefe ftates, whether that fub- 
ftance be called charcoal,, or the gravitating matter of heavy 
inflammable air. 

Hence it appears, that the phlogifticated and heavy inflam- 
mable airs combined, conftitute charcoal ; and that the mere 
application of heat always relolves charcoal into thefe two fub- 
ftance s. But the heavy inflammable air is itielf a compound 
of the lighter inflammable and phlogifticated airs. If phlo- 
gifticated air be combined with the heavy inflammable, or^, 
which is the fame thing, if light inflammable air be taken 
from it, charcoal is re-produced; therefore, when fulphur is 
melted in the heavy inflammable air,, and hepatic air formed 
in it, the remaining parts of the heavy inflammable air return 
to the ftate of charcoal. And laftly, when fulphur is melted 
in contadt with charcoal, the decompofition is complete ; and 
the charcoal is refolved into its ultimate particles, the phlogifti- 
cated and light inflammable airs, with a fmall admixture of 
volatile alkali. 

Thus far I have proceeded in the decompofition of the heavy 
inflammable air. The formation of this air, on many occa- 
fions, confirms what has been faid concerning its analyfis. In 
the refolution of compound bodies into their conftituent parts, 
it may always be fufpefled, that the whole is not accounted 
for, that fome part may have eluded obfervation, till the very 
4 . parts - 


jo Dr . Aus^in^s Experiments on 

parts we affign are put together, and the fame compound is 
produced from them. The frequent produdlion of fixed air, 
from fubftances generally not iuppofed to contain the heavy 
inflammable air, has lately given rife to a new fyftem in che- 
miftry. The author of this h fern has the merit of pointing 
out the appearance of fixed air in a 1 mo ft all phlogiftic procefies, 
in the combuftion of various fubftances, in the reduction or 
metals, and in the decompofition of acids ; phenomena which 
cannot otherwife be accounted for, than by (hewing that the 
fpecific matter of charcoal is a compound body; that its com- 
ponent parts are prefect in all thefe precedes ; and in fome of 
them nothing elfe, if we except dephlogifticated air. 

1 have already taken notice of the formation of fixed air 

from nitrous ammoniac, which is now well known to contain 

nothing, but the phlogifticated, light inflammable, and dephlo- 

crifticated airs. This fait, heated in clofe veflels, vieids de- 
£> j 

phlogifticated nitrous air in great abundance, mixed with a 
fmall proportion of fixed air. I have often repeated this expe- 
riment with nitrous ammoniac, which indicated no trace of 
fixed air either with lime water, or with acids, before its de- 
compofition ; but, when the fait was decompofed by heat* I 
always found lime water rendered turbid by the generated air; 
and, upon adding an acid to the turbid lime water, have ob- 
ferved air bubbles to be produced in it. 

When the three elementary airs are in a condenfed ftate, and 
are fet free from any combinations, they unite and form fixed 
air without the aftiftance of heat. Thus fixed air is generally 
produced when metals are diflblved in the nitrous acid. In 
thefe folutions, the component parts of nitrous acid and the light 
inflammable air, being extricated at the fame time, unite before 
they have acquired the aeriform ftate ? and conftitute fixed air. 

Objeds 


the heavy inflammable Air . 71 

Objects are often too common or too near for our obferva- 
tion. Phlogifticated air prefents itlelf in the decompofition 
of fo many bodies, that its appearance excites no enquiry ; 
and it is not regarded as eflential to the chemical conftitution. 
of the bodies which yield it, excepting in the inftances of ni- 
trous acid and volatile alkali, two fubftances of very fmall 
extent in the fcale of natural bodies. The calces of metals 
are well known to contain phlogifticated air; yet the effect of 
this air on calcination in general, and how far the very different 
calces of the lame metal are influenced in colour or other pro- 
perties by the different proportions of phlogifticated air, has never 
been confidered. Fixed air is often formed from the calces of 
metals, mixed with water, or with fome other fubfbmce contain- 
ing light inflammable air Red precipitate mixed with iron 
filings yielded very pure fixed air. Brafs duft mixed with red 
precipitate, likewife gave out fixed air, though in lefs quan- 
tity. Turbith mineral and iron filings, treated in the fame 
manner, afforded much lefs fixed air than the red precipitate 
and iron filings. It is probable, that the turbith mineral contains 
lefs phlogifticated air, than the red precipitate. The fixed air 
in all thefe experiments was mixed with phlogifticated and de« 
phlogifticated air. Mr. Kjrwan t found, that the fimple 
calx of mercury with iron filings and water produced fixed air# 
The fame author alfo obferved, that iron calcined with nitrous- 
acid gave out, upon being heated, fixed air; and he found the 
production of this air renewed upon the addition of water. 
Dr. Pr 1 3 stley j obtained fixed air from iron converted into 
ruft by expoiure to nitrous air. In all thefe experiments the 

* Priestley* VI. p. 253, 254. 
f Eflay on Phlogifton, p. 114, 

$ Ibick p. 52. 

three 


y2 -Dr. Austin’s Experiments ,. &c. 

three elementary airs are prefent, and, being expelled by heat 
from the metals with which they were combined, unite with 
each other, and form fixed air. It is not material to the pre- 
fent argument, whether the light inflammable air be fuppofed 
to be furnifhed from water, or from the regulus of a metal: 
it is enough for our purpofe, that none of the fubftances em- 
ployed in thefe experiments, contain heavy inflammable air or 
charcoal, in fufficient quantity to account for the fixed air pro- 
duced, as Dr. Priestley * has juftly obferved. 

The growth of plants affords a ftrong proof of the forma- 
tion of charcoal from the fubftances which have been affigned. 
If we may believe experiments, water and air alone are ne- 
ceflary to this natural procefs ; yet vegetation is the great fource 
of charcoal or heavy inflammable air. This enquiry is ftill in 
its infancy ; but from the beft experiments that have been made 
it fhould feern, that plants grow beft in phlogifticated air ; that 
they take in phlogifticated air, and give out dephlogifticated air. 
Thefe phenomena cannot be accounted for but by luppofing, 
that water Is decompofed by growing plants; that part of its 
dephlogifticated air is difcharged into the atmofphere ; and that 
the other conftituent part of water, with phlogifticated air, is 
taken into the growing fubftance. Thus the phlogifticated 
and light inflammable airs are brought together by the procefs 
of vegetation. 

O 

* Priestley, VI. p* 3*9* 




C 73 ] 


IX. Some Account of the Strata and Volcanic Appearances in 
the North ^Ireland and Weftern JJlands a/' S cotland. In 
two Letters from Abraham Mills, Efq. to John Lloyd, Efq. 

F. R. S. 


Read January 21, 1790, 


LETTER I. 

DEAR SIR. Fence Houfe near Macclesfield, Jan. 20, 1789® 

Y OUR requeft (hall be complied with ; I will endeavouf 
to defcribe the Whyn Dykes in the ifland of Hay, and 
give you my reafons for fuppofing them to be of volcanic ori- 
gin ; but you muft not expefl a complete and fcientific defcrip-* 
tion from me who am fo little verfed in mineralogy, and have 
fo little leifure to purfue that ufeful and engaging ftudy. 

My engagements in the mineral line were the caufe of my 
going to Ireland in 1787, to infpedt the copper mines in the 
county of Wicklow, whence I proceeded to the county of 
Antrim. 

As I performed my j’ourney through Ireland on horfeback, I 
availed rnylelf of the opportunity that mode of travelling gave 
me, to note the ftrata as I paffed along ; but (hall not trouble 
you with my obfervations till I arrived in the neighbourhood 
of Moneymore, where I firft perceived tumblers of lava; 
from hence by Maghera, Garvagh, Coleraine, Portrufh, and 
Vol. LXXX, ' L to 


Mr. Mii.ls’s Olfervathns on 

to Bufh-Mills, lava is continually feen, either in folid maftes, 
forming the bafis of the vegetable foil, or die in tumblers 
difperfed over the furface. 1 employed two days in ftudying 
the various appearances at the Giant’s Caufeway, and regretted 
being obliged to quit it fo -haftily. So much has been already 
faid upon this fpot, that 1 will only venture to rcmsik, thrit 
the red ochry joints between the beds of rude lava, and the 
different heights at which the bafalt pillars are feen, give pro- 
bability to the conjecture, that the whole mafs has been the 
produce of feveral fucceffive eruptions. 

I embarked at Port Ballintrea, and after twelve hours failing 
arrived at llay. My objed was to infpeft the lead mines which 
were open, and to view the other mineral veins in feveral parts or 
the ifland. It was impoffible to do this, without at the fame 
time noticing the Angular appearance of thofe mafles, which 
run in a kind of veins in various directions, and are called 
Whvn Dykes. As my attention was principally engrafted by 
the former, and my ft ay in the ifland very fiiort, I only cur- 
forily remarked, that the latter had in fome places a bafaltic 

y 

appearance ; but my time did not admit of a minute inquiry 
into their nature. 

On my return from Hay I landed at Portrufh; and, in 
my way to Ballycaftle, I viewed the Giant’s Caufeway from 
the top of the cliffs, and was much ftruck with feeing below 
me, in the fourth or eaftern bay, a kind of Whyn Dyke, which 
ran into the fea towards the N.N.E. 

Examining the cliffs at Ballycaftle, 1 found the horfes (or 
faults) of which there are feveral between the coals, were veins 
of lava (refembling the Whyn Dykes of Hay) ftanding ver- 
tically, interfering the various ftrata of coal and freeftone, 
and running into the fea. The largeft: of the veins or Whyn 

Dvkes 


fame Strata in Ireland and Scotland. 

u / j 

Dykes is near twelve feet in breadth, and ranges N. by E. and 
S. by W. Your fubfeqnent voyage to Raghery difcovered 
that the Whyn Dykes pervade that ifland. 

Returning to Dublin, through Clogh, Ballymena, Antrim, 
Glanevy, Moira, Ban bridge, Loughbrickland, and until within 
a (hort di dance of Newry, I conftantly faw tumblers of lava, 
and income places the fixed mafs of lava, in which were fif- 
lures ranging N.E. and S.W. 

When I reached home, my mind being ftrongly imprefled 

with the fimilitude that fubfifts between the Hay Whyn Dykes 

and thofe of Ballycaftle, which take their rife in a country 

•/ 

confefledly abounding with volcanic matter ; that I might be 
enabled to form a better judgement of their fubftance when I 
Ihould again vifit Hay, I repeatedly and attentively examined 
the Derbyshire toadftone in the neighbourhood of Buxton, and 
found it very like the fpecimens of the Whyn Dykes, which 
I had brought with me from Hay. 


Early in the laft fummer I went into Ireland, and having 
fpent fome time at the mines in the county of Wicklow I 
proceeded to Belfaft ; and a little to the northward of that 
town (near the fpot where an unluccefsful trial was fome time 
fince made for coal), I difcovered in a bank a body of marl, 
running N.E. and S.W, between red and white fand-ftone, the 
whole included and furmounted by a kind of toadftone and 
rude lava, whofe joints had no particular direction. Above 
five miles north from the town, is a mountain called Cave 
Hill (from its containing three natural caverns) ; at the diftance 
from which I faw it, the fummit appeared bafaltic, under 
which is white limeftone. 

At Belfaft I embarked for Ilay; but the wind, hanging 
to the northward, obliged us to tide along the Irifh fhore, 

L 2 ' which, 


yg Mr. Mills’s Obfervations on 

which, after pafling Carrtckfergus, chiefly confifls of ftu- 
pendous bafalt cliffs ; in which we obferved the noted feven 
caves, which are fiifures of various dimenfions going in to 
the weft ward. Farther north the cliffs are divided into ho- 
rizontal beds of conftderable thicknefs, by the intervention 
of a red fubftance, fimilar in appearance to that at the Giant s 
Caufeway ; near the water’s edge, and under the lava, the 
white limeftone is frequently leen ; and thefe appearances 
continue all the way to Red Bay. At feme diftance from the 
coaft are the Maiden’s Rocks, which, from their dark colour, 

I judge are alfo bafaltic. At the head of Red Bay, the moun- 
tains flope gradually to the fea, have a red hue, and, I am 
told, iron ore is found in its vicinity. Being obliged to anchor 
in a little fandy cove on the north fide of Cufhendun Bay, I 
landed, and found the beach fkirted with tumblers of bafaltes, 
hornftone, granite, and gneifs. In a brook is a firing of iron 
ore, half an inch thick, running north between compact 
hornftone fides. At a fmall diftance from the beach is a large 
fijfure or cavern, whofe fides are tinged red. Weftward 
from hence are very large blocks of gneifs ; but I could not 
difeover whether they compofed the firm ftrata, or were only 
tumblers : it is however to be remarked, that north from hence, 
at Murlogh, there is a bed of gneifs, whofe thicknefs, is un- 
known ; and again, four miles from Clogh ( which is S.W. 
from hence), under a bed of white limeftone, forty feet thick, 
I faw the upper part of a bed of gneifs ; fo that what is feen 
here is probably the firm ftratum. Sailing from hence, I 
plainly faw that the high broken point, which forms the N.E, 
point of Cufhendun Bay, is compofed of lava, with fome rude 
appearance of pillars near the top ; whilft clofe to the water’s 
edge, and at fome little diftance in the fea, were tumblers of 
an immenfe fize* ^ 


fome Strata in Ireland and Scotland. 77 

It was evening when we failed from hence, and in the morn- 
ing we were fo far to the northward of Raghery, as to have but 
a very imperfed view of its bafalt cliffs, whilft Fairhead and 
Ballycaftle were totally obfcured by the hazinefs of the weather. 
At length, having been four days and nights in the paffage, 
we landed at Loch Loudain, in the eaft fide of Hay. 

The volcanic country, which we exploded together in the 
ifland of Mull, having hitherto remained undefcribed by any 
traveller, I (hall now beg leave to remind you of what we faw 
there, and in our voyage to Staffa ; which may help to confirm 
my opinion refpeding the Ilay Whyn Dykes, which I (hall 
referve for the fubjed of another Letter. 

Sailing from Freeport, in the ifland of Ilay, at ten o’clock 
at night, of Wednesday, July 2, 1788, we paffed Colon fay, 
without being able to diftingui(h the fubftance of its (hores ; 
but entering the found of Iona, we faw that the rude coaft of 
Mull, and the lefs elevated fhore of Iona, was competed of 
red granite. At the landing place in Iona is laminated horn- 
done; and a quarter of a mile north from the ruins of the 
Cathedral is a vein of coarfe red granite, two feet wide, (land- 
ing nearly vertical, and ranging with the hornftone E.N.E* 
and W.S.W. ; on the furface are tumblers of red granite, and 
fome few of lava. About a mile N.W. from the Cathedral, 
and near the (hore, is a vein, two feet wide, containing feld- 
fpath and white mica, ranging E. and W. between granite (ides. 
Many of the rocks are tinged with iron, and there is fome bog 
iron ore in the modes. In the S.W. part of the ifland, is a 
body of white marble, veined with pale green. At the Cove, 
where it is faid St. Columb landed, the cliffs are of red gra- 
nite, and the (hore is covered with great variety of pebbles of 
ferpentine, bafaltes, granite, quartz, and other fubftances. The 

n:w. 


-g Mr. Mills’s Obfervations on 

N.W. part of the ifland is very rocky, affording little pafture, 
except in feme low fpots, where the loll is Tandy, and produces 
not only grafs, but likewise corn and potatoes. The whole 
extent of the ifland is three miles in length N E. and S.W. 
and one mile in breadth ; and it intirely confifts of alternate 
barren crags and little fertile vales. 

Having engaged a boat with four rowers, we went from 
Icolmkill through the Bull Sound, which runs between Nun’s 
Ifland and the ifland of Mull ; on both (ides the cliffs are of red 
granite, ragged and broken, without any regular beds or fif- 
fures, and having no particular range or inclination. Hence 
we fleered for Ardlun Head, which forms the S.W. point of 
Loch Leven. When we approached the Head, we flopped 
the rowers, and fat fome time contemplating the wonderful 
arrangement of the bafalt columns ; and, as we again rowed 
along fhore to the eaftward, had a fine view of the various 
fituations into which the columns were thrown. The coaft 
being every where fteep, it was fome time before we could find a 
convenient place to land , but having at laft got on fhore, we 
walked to the extreme point or head : here, ftruck with the 
errors of our maps, which placed the iflands in fight very dif- 
ferently from their true fituations, I took the following bear- 
ings by the compafs. 

TheN.E. point of Iona N.W. by W.—TKe Dutchman’s Cap 
N.N.W. — Cairnborough N. by W.— Staffa from N. to N. i W. 
diftant, by eftimation, about three leagues. — Rhu Thalve, the 
northernmoft extreme of Mull, N. by E, — Inch Kenneth 
N.E. i N. — The point of Ben Vawruch, on the north fide of 
Loch Leven, N.E. diftant, by eftimation, three miles. — The 
range of Loch Leven E. by S. and W. by N. 

6 


About 


fome Strata in Ireland and Scotland. jg 

About a-quarter of a mile from the fpot where the bearings 
were taken, is a deep glen,' running N.N.E. to the fea. It is 
about* thirty yards in length, and twenty in breadth. The 
flrata are diipofed in the following extraordinary manner. The 
uppermoft is ten yards of lava, with horizontal divifions and 
vertical joints, taking the form of rude pillars. Under this is 
an horizontal bed of a perfectly vitrified fubftance, which ap- 
pears to have been a fihale, and is from one to two inches in 
thicknefs. Beneath this, is about three yards of a filiceous 
gravelly concrete ; below which are horizontal beds of indu- 
rated marl, of various thickneftes, from fix to twelve inches. 
The whole of thefe beds, taken together, are about four yards, 
and there is a large fiffure in them, on the weft fide of the glen. 
Laftly, are ten yards of rude lava, containing fpecks of quartz 
and mica unaltered, pieces apparently of granite, and fome 
nodules of calcined chert. The whole is incumbent on regular 
bafalt pillars, of various dimenfions, from eighteen to fix 
inches diameter, varying in the number of their fides, fome 
having five, fome fix, and others feven fides. They are alfo 
as varioufly difpofed ; thofe on the weftern extremity of the 
glen being ftraight, and lying horizontally ; whilft of thofe 
on the eaft fide fome are bare, and ftanding perpendicularly ; 
and others, which are furmounted by the rude lava, are in- 
clined and curved, as if they had taken that form in cooling 
from the preffure of the incumbent weight. See Tab. IV. fig. i. 
Many of the pillars are very full of bladder- holes ; the articu- 
lations of the joints are clofe, though not fo clofe as thofe of 
the Giant’s Caufeway ; but, like thofe, their tops, where ex- 
pofed, are either concave or convex. 

At the extremity of the glen is an infulated rock, fupported 
by bafalt pillars (fig. 2.), which are fomewhat curved and 

inclined. 


g Q Mr. Mills’s Ohfervations on 

inclined. Incumbent on thefe are other pillars, lying nearly 
horizontal, and having a rude face of lava to the wefhvard. 
At high-water this rock is inacceffible without a boat ; but at 
low water it may be eafily got at, by ftepping from one tum- 
bler to another ; and on the north fide it is not difficult to climb 
to the top. The bottom of the glen is covered with large tum- 
blers of lava the whole way down to the rock, and prefents 
the rudeft fcene imaginable. 

-Oppofite Ardlun Head, on the north fide of Loch Leven, is 
Ben Vawruch, an high promontory, whofe ftrata are in Hori- 
zontal beds ; and the hill being of a circular figure gives it the 
appearance of having feveral terraces, with a kind of cattle or 

cairn on the top. 

The columnar pillars at Ardlun are more or lei s regular for 
an extent of near a mile and an half ; and all the projecting 
points of Loch Leven, as far as the eye could reach., appeared 
to be compofed of lava. 

Amongft the rude lava, which forms the bafis below high- 
water mark, are nodules of cryftal and agate, adhering in 
fmall lumps to the rocks ; but, being blackened by the watlnng 
of the fea, are not to be difcovered without a very nice fearch. 
Our boatmen informed us, that higher up the Loch there is a 
bed of coal. This we wifhed to fee ; but, as they alfo told us, 
that the weather, which had for fome days paft been very tem- 
peftuous, was now favourable for landing on Staffa, we deter- 
mined to avail ourfelves of the opportunity, and got into the 
boat, highly pleafed with what we had feen ; and for which 
pleafure we were indebted to the hint in Dr. Johnson’s Tour 

to the Hebrides. _ ~ 

We landed without difficulty on the eaftern fide of Staffa, 

and on an eminence, near the center of the illand, I obferved 


i 


fame Strata in Ireland and Scotland. 8i 

the following bearings. The Dutchman’s Cap N.VV. — Cairn- 
borough N. by W. — The Paps of Jura (over Mull) S. by W. 

The greateft extent of the ifland is about one mile from 
N.E. to S.W. and in one part not more than a quarter of a 
mile from S.E. to N.W . It is tolerably level, the fhore every 
where fteep, and the cliffs formed by bafalt pillars or rude lava. 
The ufual landing place for boats is in a fmall cove on the 
N.E. fide of the ifland ; but we were affured, that there is no 
anchorage for veffels round its whole coaft. On the fouth fide, 
rifing from a nearly horizontal bed of reddifh ftone, are beautiful 
bafalt pillars of confiderable height, and {landing vertically ; at 
a little diftance are others inclined, and others which are 
curved, very hmilar to the ribs of a fhip. 1 here are three 
caverns amidft the bafaltic pillars ; the northernmoft goes in to 
the eaftward, how far I know not ; for, though we went en- 
tirely round the ifland in our boat, the tide was too high, and 
the fwell too great, to permit our entering any % of the caverns 
without the utmoft rifk ; we therefore forbore to make fo 
dangerous an attempt. One of the caverns is now u finally 
called Fingal’s Cave ; but the fchool-mafter at Icolmkill in- 
formed us, that the Erfie name for it is Fein, which fignines 
the melodious or echoing cave. On the northern part of the 
ifland, and at the cove where we landed, the cliffs are of 
coarfe lava, without any pillars. In fome parts of the ifland 
the tops of the pillars are ftanding bare ; in other parts the fur- 
face is formed by a rude argillaceous lava, full of bladder- 
holes, fome empty, others replete with quartz cryftals. Calca- 
reous fpar, pebbles of indurated clay and fhoerl, detached 
pieces of zeolite, are frequently feen, and the vegetable foil is 
a decompofed lava. In fome places we met with gravel con- 
taining pebbles of bafaltes, of red granite, and of quartz, 
Vol. LXXX. M whofe 


Mr. Mills s Ubjervattons on 

whofe angles were worn off, and they were become round and 
fmooth. On the N.W. fide, the cliff has lately given way ; a 
large portion of it has fallen into the fea, and a ftill further 
part appears likely to follow it. 

On the ifland are two fprings of excellent frefh water. 
There were three houfes (July 5, 1 7 3 8 uninhabited; and 
barley, oats, flax, and potatoes, growing near the center, and 
good grafs in feveral fpots. When the crops are ripe, la- 
bourers are fent to gather them in ; after which, thirty head 
of cattle are fent to winter in the ifland, which, w: th a foli- 
tary herdfman to attend them, continue till feed-time the 
en filing fpring. 

In attempting to return to Hay, after having got within 
three miles of the N.W. part mf Coloniay, an heavy gale of 
wind came on, which obliged us to bear away, and take flhel- 
ter in the Bull Sound. The weather continuing ftormy, we 
landed, and walked to Fidden, the houfe of Lieut. Col. 
Campbell, of the Plymouth diviiion of Marines, who re- 
ceived us with the utmoft cordiality, and hofpitably enter- 
tained us for five days, which we were detained by an adverfe 
wind and fe verity of weather. Availing ourfelves of this de- 
lay, and of Col. Campbell’s polite offer to be cur guide, we 
fet out on foot with him and Lieut. Stewart, to view the 
fleam, of coal on the fouth fide of Loch Leven. After palling 
fome moory ground, and continuing our route to the northward 
for an hour and an half, we came to a fpot where the rock which 
puts up to the day is a laminated micaceous ftone ot the gneiis 
kind (Kir wan, p. 102.); and in another half hour, near a 
fmail town on the S.W. fide of Loch Lyne, we were fhewn a 
quarry where the gneifs ranges N.E. and S.W. and has a flight 
hade to the S.E. It is in ribs from two to twelve inches thick, 

and 


fome Strata in Ireland and Scotland. 83 

and is ftratified by intermediate ribs of red granite of about an 
inch thick. We crofied Loch Lyne in a boat, and landed on a 
rude mafs of lava, which continues away to the N. E. by the 
town of Ardlun, and onwards to the S.W. fide of Loch Leven. 

In a fmall bay, about one mile to the S.E. of Ardlun Head, 
under a bed of jointed lava, which has fome refemblance of 
pillars, and juft at high-water mark, is a bed of coal, exaftly 
tw r elve inches thick, intermixed with fhale or bituminous 
fhiftus (Kirwan, p. 89.) dipping S.E. towards the Loch one 
yard in three : there is not any intervening fubftance between 
the coal and fuperincumbent lava, which contains many blad- 
der holes. Beneath the coal is alfo lava without any inter- 
vening matter. About twenty yards to the N.W. the coal 
again appears in the cliff, but is not more than from eight to 
ten inches thick. Here are tumblers of various fizes, feat- 
tered on the fliore. Amongft them are iome refembling the 
Derbyfhire toadftone ; and a fhort diftance inland (to the S.W.) 
are rude maffes of lava, {landing up at day, not unlike the great 
Whyn Dykes of Ilay. In the Loch, and at fome diftance 
from the oppofite fhore, there flood, within the memory of 
man, an infulated pillar of coal, from which the country peo- 
ple w r ere accuftomed to procure a fupply for fmiths ufe; but 
the quantities they carried away, and the continual waffling of 
the fea, have now entirely removed it. 

We returned to Fidden Houfe, which is fituated on level 
ground near the fea, and near a fmall Loch, which affords an h ar- 
bour to fmall veifels, but is dangerous to enter. The flat country 
in front of the houfe is entirely compofed of fea fand, including 
Ihells : when dug into, frefh water is conftantly found at a few 
feet below the furface. At the back of the houfe, towards 
the fea, are cliffs of red granite, which extend round .to the 

M 2 Bull 


5 4 Mr. Mills’s Gbfer*uatwns on 

Bull Sound. On the (bore are pebbles of bafaltes, of granite, 
and of gneifs ; and from the firm rocks we collected feveral 
fpecimens of granite, in which the feldfpath, quartz, and 
black mica, are differently blended, but without any (hoerl. 

During our flay at hidden, I learned from Mr. Stewart^ 
that Rhos Mull, which is the N.W. part of Mull, is chiefly 
red granite: in the fouthern part of the ifland is very fine- 

white freeftone, and between that and the granite ail whyn- 
ftone. The ifland of Lifmore, in the found of Mull, is in- 
tirely limeftone, excepting where it is croffed by the Whyn 
Dykes. In the ifland of Uiva are pillars fomewhat refembling 
thofe of Staffa, but of a paler colour. — Canna alfo is bafaltic, 
and refembles Staffa, — The Dutchman’s Cap has rude pillars - — 
Cairuborough the fame. Dunvegan in the ifle of Skye has 
bafaltic pillars, fimilar to Staffa. — On the fouth-weft fide of 
the ifle of Egg is a curious cavern. 

We again embarked for Hay ; but, it being calm, and the tide 
againft us, were obliged to anchor ; and we landed on an ifland 
which forms the S.E< point of the found of Iona. From the 
point, which is a bare rock of red granite, broken and jointed 
in every direction, I obferved the following bearings. Icolm- 
kilm Church N.N.E. — The northernmoff part of Stafia, over 
the N.K. point of the found of Iona, N.E. by N. — The fouth 
Pap of Jura, over Colonfay, S. 

The upper furface of the granite, even in the very higheft 
part, is all convex, which feems to prove, that by fome con- 
vulfion it has been thrown up from the bed of the ocean* 
which, by long wafhing over it, had previoufly worn down its 
fiibftance at the edges of all its numerous joints. On the eaft 
fide of the point, and on the weft fide of a little bay, where 
the granite cliffs are at leaft fifteen yards perpendicular, we 
i . difcovered 


fame Strata in Ireland and Scotland. 85 

difcovered a Whyn Dyke, or vein of lava% about two feet 
wide, included in a vertical fiflure ranging S.B. by E. and 
N.W. bv W. Going round to the oppofite fide of the bay, 
we found the lava on the cliff ranging as above; but the vein, 
or Whyn Dyke, much fmaller, being only from eight to ten 
inches between the granite fides, which feemed to continue 
doling ; nor could it be feen on the main land of Mull, which 
was at no great diftance. The fiflure, which includes the lava* 
is, where firft difcovered, wider than the vein of lava it contains,, 
which therefore Hands wholly detached from the SfW. fide. 
The lava and fiflure range quite through the point; and to 
the N.W. by W, on the oppofite fide of a fmall found or 
inlet, it appears on a rocky ifland, divided into two veins,, ftilli 
keeping nearly the fame direftion. 

About fix yards to the weftward of the lava vein, or Whyn 
Dyke, is an i m men fe fiflure in the granite, ranging N. by W* 
and S. by E. It is from nine to ten feet wide, and, by efti- 
mation, about an hundred and twenty feet deep. At the 
northern extremity, near the top, two ftones are fufpended in 
a moft extraordinary manner between the fides : the under one 
is fixed, and upon that the other appears to lie loofe. (See fig*. 

There is a large cavern m the weftern fide of the fiflure^ 
and a correfponding fiflure is ieen on the oppofite Chore* 

In the evening, when the tide favoured us, we failed. The 
night proved calm and foggy, and in the morning we found our- 
felves near the weft coaft of Jura, to the northward of Loch 
Tarbut. As we approached the Chore, we found it rocky for the 
diftance of a quarter of a mile from the cliffs, which are low, and 
apparently of chert. Being quite calm, we rowed along fhore^ 


# See Magellan’s Cronftedt, p. 916, 


pafled 


86 Mr . Mills’s Objervations on 

paffed the entrance of Loch Tarbut, and obferved feveral 
Whyn Dykes, or lava veins, running into the fea. The 
Paps of Jura were moftiy covered by the fog ; but which 
breaking away at intervals gave us a view of their lofty fum- 
mits, and of the narrow ftripe of rock mentioned by Mr. Pen- 
nant (Voyage in 1772, p. 21 7.), called the Hide of the Old Hag, 
to which is annexed a curious legend ; but which, in reality, ap- 
pears to be the furface of a Whyn Dyke, running down the 
fide of the x cherty Mountain. After entering the found of Ilay, 
obferving a very confiderable Whyn Dyke, or vein of lava, on 
the Jura Ihore, we landed, and found it range N.'N.W. and S.S.E. 
It is of a dark colour and compad texture, and in fome parts will 
give fire with fteel. Near to this Whyn Dyke is a red argil- 
laceous fubftance, ftrongly impregnated with iron, and con- 
tained in an inclined ftratum, varying in thicknefs, and termi- 
nating in a cavern, whofe fides and roof are of the fame fub- 
ftance, but wonderfully broken and thrown into every direc- 
tion, as is the including chert, amongft which we found fome 
that is brecciated. 

Soon after we returned to our boat, a fquall of wind came 
on, attended with heavy rain, which almoft wholly obfcured 
each (hore, and continued till we landed at Freeport, wet and 
fatigued, but highly gratified by the recolledion of the many 
curious objeds we had vifited during our excurfion. 

It having been confidered as very extraordinary, that a bed 
of coal ftiould be found, as at Ardlun, incumbent upon, and 
furmounted by, a mafs of lava ; I was induced to look into 
fome of the authors who have treated of volcanic countries ; 
and find there are many inftances of coal in the vicinity of 
lavas, though I have not met with any precifely fituated like 
the coal at Ardlun. 


May 


fotne Strata In Ireland and Scotland. 87 

May not the coal found at Ardlun be an indurated bitu- 
men, which, exuding in a liquid ftate from the incumbent 
matter, penetrated the argillaceous fhiftus, which previ- 
oufly conftituted the intervening ftratum between the lava ? 
It has fome of the properties of jet ; the fpecific gravity of 
that which we procured is 1,284; it is of a glofly black, its 
fradure glafly and conchoidal, does not foil the .fingers when 
handled, and when warmed by fridion will attract light bo- 
dies. Placed on a red-hot iron it decrepitates, emits a denfe 
fmoke which has a refinous fmell, becomes thoroughly ignited, 
burfts into flame, and yields an impalpable refiduum, which is 
not attraded by the magnet, and of which I only procured 
half a grain, of a yellowifh brown colour, from twenty grains 
of the crude fubftance. 

The learned Bifhop of Landaff, in the third volume of 
his Chemical EflTays, in his Effay on Bitumens (p. 6.), fup- 
pofes that, under certain circumftances, naphtha, petroleum, 
and afphaltum, might be produced by a kind of fubterraneous 
diftillation, and might impregnate the porous ftrata of feveral 
kinds of ftones and earth. Confider then, whether the fub- 
ftance I have been defcribing may not have been produced in 
that manner, Alice it is included within a mafs of matter 
which carries every appearance of having formerly been aded 
upon by fire. 

I am, &c. 

A. MILLS. 

P.S. If you compare the bearings which I have taken with 
the map in Mr. Pennant’s Voyage in 1772, they will be 
found to agree ; and if the variation of the needle be allowed, 
they will coincide with the map in Dr. Anderson’s Prefent 
State of the Hebrides. 

5 


LET- 


Mr. Mills’s Obfervation-s oh 


88 


LETTER IT. 

BEAR SIR, Fence Houfe, Feb. I, 1789. 

HAVING in my former letter (hewn, that Whyn Dykes, 
or, in other words, veins of lava, are found in the vicinity of 
columnar bafaites, which latter are now, by almoft univerfal 
confent, acknowledged to be of volcanic origin ; I (hall pro- 
ceed to defcribe the Whyn Dykes of Hay, and (hall commence 
with giving you a general idea of the extent and various ftrata 
of that ifland. 

Ilay, from the northern to the fouthern extremes, is about 
thirty miles in length, and in one part extends nearly as much 
in breadth from the eaftern to the weftern fhores. The S.W. 
part of the ifland is low ; but the land rifes to the N.E. and 
the mountains and cliffs which form the north-eaft coaft are 
fteep and lofty. At the head of Loch-in-Daal, and near Bo- 
more, the rock which appears at day is of curled hornffone, 
and does not feem to have any particular dire&ion. Purfuing 
the road (N.E.) to Port Afkeg, the hornffone becomes more 
regularly laminated, and ranges N.W. and S.E. ; and fome of 
the hollows between the little riling hills are found to contain 
gravel. At four miles from Bomore commences the limeftone 
ftratum, the joints in which are nearly vertical, and range in 
general N.E. and S.W. It is about four miles in breadth 
from S.E. to N.W. ; but I have not been able to difcover how 
far it extends in the courfe of its range, never having traced it 
more than three miles in that direction ; but it is nearly certain, 
that it does not reach either the eaftern or the weftern fhore, 

from 


fome Strata in Ireland and Scotland. ty 

from the Mull of Kinhouth, the eaftern fide, being hornftone 
till near M‘ Arthur’s Head ; and from thence, round to the weft- 
ward, the cliffs being of chert. Continuing the route for 
almoft a mile along the high road, after leaving the limeftone, 
veins of fliale, and of a whitilh ftone marl, are feen ; then 
the chert appears, which reaches to Port Aflteg, and north and 
fouth from thence along the fhores of the found not only on 
the Ilay but likewife on the Jura fide. Within the ifland are 
feveral fmall lochs (or lakes) and many turf mofles. Where 
the limeftone prevails are fome minute ftrings of rich copper 
ore, and mines are opened in lead ore veins y but they are not 
productive of profit to the adventurers. There are many old 
workings, fuppofed to have been opened by the Danes. Iron 
ore is found ftratified in the mountains. Bog iron ore is met 
with in the mofles , and near Bally-echra is a body of form 
iron ore. At Loch Knock, near M‘Arthur’s Head, is an 
"extenfive bed of gneifs ; and near Ardleftree is an immenfe 
Whyn Dyke, and the hill Knock Reneftle is a magnetic 
mafs of rock, which confiderably deranges the compafs, as you 
difcovered when you vifited it laft fummer. 

The Whyn Dykes are too fingular in their formation to 
efcape the eye of the naturalift who traverfes this ifland. Thev 
are mafles, or rather veins, generally of a dark-brown (appa- 
rently bafaltic) matter, not unfrequently containing bladder- 
holes ; from three, four, and fix feet, to eight or more yards 
in breadth, running in various directions. In fome places they 
are ftraight for a confiderable length ; in others, their courle, 
though progreflive, is infleCted ; and in fome parts they rife 
between three and four feet above the furface, forming natural 
boundaries or dykes (from whence their name feems to be 
\ ol. LXXX. N derived) 


w> Mr. Mills's Obfervations on 

derived) Handing vertically, and appearing to fill up the chafms 
formed at fome remote period in the ftrata. 

In giving a more minute account of the Whyn Dykes which 
have fallen under my obfervation, it becomes neceffary to men- 
tion, that when I arrived at Loch Loudain, I there hired a 
row boat, in which I proceeded to Freeport Bay* At the place 
where I re-imbarked, the fhoreis low, and compofed of horn- 
ftone. After paffing the ruins of an ancient caftle, in about 
an hour and an half I landed on a rocky point, where I difco- 
vered a large Whyn Dyke, between three and four yards wide, 
Handing vertically, and ranging S. W. into the land* It is of 
a dark-brown colour, externally approaching to black, and 
contains bladder-holes, fome of which are filled with quartz, 
and others with reddifh lamellar fpar, which effervefces ftrongly 
with nitrous acid, as do many parts of the bafis of the fub- 
itance, which is too foft to flrike fire with Heel, but is confide- 
rably magnetic, and of the fpecific gravity of 2,863. Embarking 
from hence, and eroding a fmall fandy bay (named Thu rot’s 
Bay, from that gallant Frenchman having landed there), we 
reached the high mountainous point called McArthur’s 
Head, which forms the S.E. point of the found of Ilay. The 
ftratum here is white chert, with many large patches and 
{tripes of red, which indicate that it contains iron ; but the 
great height, and almoft perpendicularity, of the cliffs, pre- 
vented my minutely examining them. From thence to Port- 
aikeg and Freeport Bay, the rocky fhore, which is compofed 
of chert, is lefs elevated, fhews many indications of iron, and 
has feveral fiffures and caverns ; and in fome places has Whyn 
Dykes burfting through it, which appear tore-enter on the 
oppofite cherty fhore of Jura. 


About 


Jotne Strata in Ireland and Scotland. pi 

About two hundred yards north from Freeport Lodge is a 
Whyn Dyke, which ranges N.W. andS.B.,and appears in that 
direction on the Jura fhore, which is more than a mile did: ant. 
Th is Whyn Dyke is bare at the cliffs feveral yards in height, 
and is near nine feet in width. It confifts of an inner part of* 
a granular and fomewhat porous texture, of a dark grey co- 
lour, with flbining parts like mica, includes opaque zeolite 
fpecks, and its fpecific gravity is 2,81 1. On each fide of this, 
and divided from it by fiiiall vertical fuTures or joints, not more 
than an eighth, or at the moft a quarter, of an inch wide, are 
two bodies, each near eighteen inches in width, of a dark co- 
lour, much refembling the preceding fubftance, but without 
the zeolite fpecks; the fpecific gravity is 2,850. Both the 
outer and inner fubftances (lightly effervefce with the nitrous 
acid; both are magnetic, and both give fire with fteeh The 
whole mafs is interfered, at various diftances, by lateral joints, 
and is included between the chert rock, which does not appear 
the lead altered where it comes in contaQ: with the Whyn 
Dyke. Farther along the fhore is a cavern in the chert; the 
entrance is low and narrow, but within it is very capacious. 

Intending to vifit the cave Ea mawr, on the weftern fide of 
the ifland, I took boat at Freeport, and rowing along fhore, 
which is of chert, I obferved feveral fiffures or caverns in the 
cliffs, and many Whyn Dykes, lome ranging N.W., others N.E. 

I landed, within the found, on a white fhingly beach, the ftones 
of which are all chert, rounded by attrition, and the fhingle is 
thrown up fo much above the prefent high-water mark, that 
it affords ftrong reafon to believe, that the fea has greatly re- 
ceded from thefe fhores. Above the beach, the cliffs are of 
chert. From hence I walked three miles over moors and open 
paftures acrofs the north- weft point of the ifland, and in fome 

N 2 of 


92 Mr. Mills’s Obfervations on 

of the hollows between the hills met with beds of ftones, 
fimilar to thofe I had feen on the beach. Approaching the 
weftern ftiore, Ifaw a cavern, whofe mouth opened to the eaft- 
ward, and whofe bottom was covered with water. Pafting 
this, I arrived at a narrow fteep path, which leads down the 
cliffs to the fhore. Here are feveral caverns, whofe general 
range is S.E. into the cliffs, which are compofed of chert. 
South from thefe caverns, in travelling the fandy fhore, I paffed 
a vein of laminated hornftone (approaching to the nature of 
a fhiftus) containing pyrites in the joints of the ftone, which 
range nearly N.N.W. and S.S.E. Farther fouth is an immenfe 
Whyn Dyke, burfting from the cliffs; it {lands vertically, is 
many yards in heighth, projects from the cliffs to the north- 
weft ward, and in that direction runs many fathoms into the 
fea. It bears the buffeting of the waves of the Atlantic Ocean 
from the fouth- weft, and feems to defy their rage, though its 
breadth, compared with its height and length, is very incon- 
siderable, it not being more than five or fix yards wide. It is of 
a dark granular fubftance, very fimilar to the Whyn Dyke 
near Freeport, excepting that the central part is fofter and of 
a paler colour. The outer fides, which are each about two 
feet thick, are of a very dark colour, hard, contain fome blad- 
der-holes and fpecks of zeolite, are detached from the center 
(in general) by very fmall joints, and the whole is divided by 
tran fverfe joints into irregular polygons of various dimen fions. 
If this ftupendous objedt is viewed from the north, it has 
much the appearance of a lofty wall of human fabrication. 

A fmall diftance more to the fouthward is the great cave, in 
the Erfe dialed!: called Ea mawr. The entrance is near twenty- 
three yards wide, and from fix to eight yards high. After 
going in a little way the roof rifes, and the cavern extends in 

4 breadth ; 


fame Strata in Ireland and Scotland. 

breadth ; but at about an hundred and fifty yards from the 
entrance, all its dimenfions are contracted, and it becomes fo 
finall as barely to admit further progrefs without crawling on 
hands and knees. There are fome calcareous flalaCtites pen- 
dent from the roof ; and in this cave, as well as thofe before 
mentioned,, wherever the water pervades through the joints of 
the chert, it tinges the fides of a ferruginous hue. 

From hence I returned by the fame route to the boat and to 
Freeport ; and having given you an account of the principal 
Whyn Dykes which I examined on the fea coaft, I will pro- 
ceed to relate thofe obfervations which occurred in my proorefs 
through the interior parts of the ifland, confining my remarks 
more particularly to the Whyn Dykes which conftitute the 
fubjeCt of prefent confideration. 


Afcending the hill from Freeport, in the way to Shinegarr. 
the road goes for about a mile over chert. Near Perfabus are 
beds of Hone marl, and a very large Whyn Dyke, rano-- 
mg N.E. and S.W. Hence the path leads over hornftone ; 
and in one part is a laminated hornftone, ranging E. and W. 
It inclines to a Ihiftus ; but where it Hands bare at day, is foft 
and partly decompofed ; but probably might be found ufeful 
for coverings, if it was tried in depth. Again the chert is 
feen, and again hornftone, in Which is included the lead vein 
of Shinegart, fituated on the S.E. fide of Portnealin Loch. 
Tins vein had been formerly worked ; but, when the old work- 


ings were cleared out, was found not worth purfuing. The 
vein ranges N.N.E. and S.S.W., is two feet wide, and hades, 
to the eaftward, and is crofled at right angles (a few yards to 
the northward of the workings) by a fmall Whyn Dyke. At 
Mullrees are old workings on a lead vein, which is about four 
feet wide, but left poor, and ranges N. and S. between lime- 


ftoil£ 


, • Mr. Mills’s Obfervations on 

ftone Tides, hading to the weftward. South-fouth. weft from 
hence is a natural cavity in the limeftone, called the Giant s 
Hole. Here the joints of the limeftone range S.E. and NAV . 
and are croffed by a (hale firing, three feet wide ranging N. ' • 
and S.W. The water of a little ftream, which tails into the 
Giant’s Hole, paffes through a fiffure in the limeftone, and 
ifi'ues again to the day in lower ground, fifty yards to the 
fouth-eaftward. Returned by Perfabus to Freeport, having 
gone over feveral Whyn Dykes of various widths, and run- 

ningr in various directions. 

From Freeport went (by Perfabus) to Gartnefs lead mine 
which is fituated in the center of the limeftone country ; muc i 
work has been done here, but at prefent there are no great 
profpefts of fuccefs. The principal vein, which in tome pairs 
is about one foot wide, has a flight hade to the north-eaftward, 
and ranges fouth-eaft and north-weft, along the fide of an 
immenfe Whyn Dyke, between which and the hmettone it is 
included, the points of the latter running north-eaft and fouth- 
weft at right-angles with the vein and Whyn Dyke. _ 

This Whyn Dyke is the largeft I have yet feen, being 
twenty-three yards wide. Where cut through, from Abel s to 
HodefonV fhafts, it divides the limeftone ftrata, and is near y 
vertical, having, like the vein, a very flight hade to the nort i- 
eaftward. It is chiefly compaft, but not entirely without 
fiflures. It varies both in colour and texture ; in fome part, 
approaching to the texture and hardnefs of bafaltes ; m ot «rs, 
b eL granular, of a black iron-grey colour with fhming pan., 
givef fire with fteel, is flightly magnetic, does not effervefee 
with nitrous acid, and its fpecific gravity is 2,631, O he 
parts, of nearly the fame texture and colour, have none 
of the preceding qualities; fpecific grayity 2,69b. Some 


2 


Jome Strata in Ireland and Scotland. . 

pieces are found which contain minute fpecks of fhoerl 
and of a calcareous fpar ; fpecific gravity 2,484. I n fome 
parts it is of a whitifh grey calcareous fubftance, fpecific 
gravity 2,542 ; in others of a pale greenifh grey, whofe 
lpecific gravity is 2,322, and which does not effer- 
vefce Wlth nitrous acid, but contains threads of calcareous 
fpar, and is fometimes alfo found coated, and fometimes 
fpangled, with pyrites, and then its fpecific gravity is j n . 
creafed to 2,833. Throughout this great mafs, nodules 
of a yellowifh grey colour are found, which do not effer- 
vefce with acids, or give fire with fteel, and which are in 
appearance very fimilar to fome kinds of Derbvfhire toadftonc • 
fpecific gravity 2,652. Other nodules are alfo met with’ 
of a kind of indurated clay, coated like the geodes, and tinged 
with iron. The central part, which is the fofteft, after befoo- 
drawn up, and lying fome time expofed to the affion of the 
air, decompofes, and moulders into a friable earth, fimilar to 
that which is found on the furface near Belfaft, and various 
other places in the county of Antrim, and in the ifland of 

Going from Gnrtnefs to the lead mines at Ardaehie, I paffed 
afgow Beg, where is a lead vein, formerly wrought, ranging 
between limeftone fides E.S.E and W.N.W. : a fmall Whvn 
yke croffes this vein, running nearly S. 3 .W. and N.N.E.. 
arther fouth is an old open caft in a lead vein, ranging E.* 
and W., and hading S. At fome diftance from hence is Arda- 
ch.e mine. This vein, which has formerly been much 
wrought has the fame range and hade as the preceding, and 
is crofied by a Whyn Dyke, ten feet wide, which throws the 
vein nine feet from its general diredion. Proceeding from 
nence over moory ground, near Allala, faw a dead vein of 


^5 Mr. Mills s Obfcrvations on 

{par, iimeftone, and an argillaceous fubftance mixed with 

mica; the whole tinged with iron. Continuing my walk, 

. •* 

I arrived at the foot of Beu Vinkie, which is compofed of a 
granulated whitifti chert. This mountain is faid to be the 
higheft in Hay. It is very fteep on the S.W. fide, where I 
afcended it by following the courfe of a Whyn Dyke, which 
reaches very near to the fumrait. This Whyn Dyke is fimilar 
to thofe before mentioned. It confifts of a dark-grey granular 
fubftance, which does not effervefce with nitrous acid, but 
gives fire with fteel, is {lightly magnetic, and its fpecific gra- 
vity is 2,901. It confifts alfo of a very dark granularfubftance, 
with the fame properties as the foregoing; and further, in 
fome parts, it has a granular fubftance, which includes fmall 
pieces of white chert ; other parts are of an argillaceous fub- 
ftance, fomewhat refembling hornftone, and others of a cal- 
careous fubftance which {lightly effervefces with nitrous acid. 
Here is alfo a kind of vein, containing a brown i(h argillaceous 
fubftance, and reddifti cubical calcareous fpar. The very fum- 
mit of the mountain is compofed of white cryftalline chert, 
which is not unfrequently tinged with iron. 

Loflit Hill being an objedt of great curiofity, I {hall with 
pleafure retrace our walk from Gartnefs by Glafgow Beg to 
Loflit Loch and to the Hill. Walking on the weftern fhore 
of the Loch we faw a vein of blue fhiftus, many yards wide, 
ranging N.E. and S.W. ; not far from which is an ochraceous 
earth, and much bog iron ore. Obferving, on the fouth fide of 
the Loch, the appearance of an ochry earth, we went round to 
examine it ; and near it we found an immenfe Whyn Dyke, 
ranging nearly S.E. and 1 M.W. compofed of a friable fubftance 
containing zeolite, of a black granular fubftance which gives 
fire with fteel, and a yellowifh grey fubftance, perfectly fimilar 


fome Strata in Ireland and Scotland. 


97 


in appearance to that before deicribed. In its vicinity the chert 
is extremely broken and cellular; and I am of opinion, that 
this is a continuation of the Gartnefs Whyn Dyke, it having 
the fame range, and nearly the fame breadth. After viewing 
the Fort (fee Pennant’s Voyage in 1772, p. 219.), we be- 
gan our examination of the fubftances which compofe the hill. 
They are in general filiceous, varioufly blended ; the northern 
brow is of chert, the joints of which range E. and W. and 
the beds are in fome parts vertical, in others horizontal. Here 
is an irregular bed of iron ore, called emery by the inhabi- 
tants ; it is from fix to twelve inches in thicknefs, and may be 
traced about four fathoms in length. Above it is a flrange 
mixture of chert, hornftone, and friable yellow fand-ftone, 
blended together without any order or regularity. This bed of 
iron ore is vifible on the S.W. part of the hill, where it is 
near two feet thick, is ftratified with the chert, which lies in 
beds from three inches to two feet in thicknefs, and is covered 
with a cryftalline fand. On the fouth fide of the hill, where 
a trial has formerly been made for iron ore, there are feveral 
lumps collected in an heap, but no appearance of bed or vein. 
Where the rock has been laid bare, it is an hard chert, with 
an outer coat of foft yellow fand-ftone. Higher up the hill is 
an hard chert, with a kind of bladder®holes. Skirting the 
hill we defcended on the north fide, and faw two places, for- 
merly wrought, where there is not any appearance of a vein, 
but merely a jumble of iron pyrites. At a very fmall diftance 
from hence, the limeftone fhews itfelf, and trials have been 
made for lead ore. Having furrounded the hill, and examined 
it attentively, and having feen the chert, of which it is chiefly 
compofed, thrown into an infinite variety of forms ; in fome 
parts broken and indented, with a kind of empty bladder- 



O 


holes ; 


q§. Mr. Mills’s Objervatiom on 

holes ; whilft in other parts they are filled with a cryftalline chert, 
with which the tops of the neighbouring mountains, and the 
Paps of Jura, abound: in Ihort, from the very rude and irre- 
gular appearance of the fummit of the hill, from its rifing fo fud- 
denly from the limeftone ftrata, and from the Whyn Dyke 
which runs through it, and which may be traced ranging far 
away to the north- eaft ward, I am ftrongly induced to believe 
it of volcanic origin. 

If it be admitted that I am right in my opinion of the vol- 
canic origin of thefe different fubftances, a large trad will 
then be added to that already proved by others to have been 
fubjed to the effeds produced by fubterraneous fire ; which, as 
far as has hitherto been difcovered with us, commences in tiie 
S.W. part of Derbylhire, and, if I miftake not, is again feen 
in Seathwaite, about five miles from Hawklhead, in the N.W. 
part of Lancafhire, and appears (N.W. from thence) in the 
neighbourhood of Belfaft in Ireland, and ranging through the 
northern part of that kingdom ; it is perceived in feveral of the 
weftern iflands of Scotland, extending as far north as tne 
ifland of Lewis, which is the northernmoft of the Hebrides, 
and croffing eaft from Hay (which is the fouthernmoft) by 
Tarbut, Dumbarton, Stirling, and Edinburgh to Dunbar. 

Some perfons may confider, with aftonifhment, the extent 
of thole veins and mafies of lava which appear in the northern 
part of the Britilh ifles, where no crater is vifible ; whilft 
others, who have read Von Troil, and recoiled that he fays 
(at p. 234*), “ That lava is feldom found near the opening of 
“ a volcano, but rather tuff, or loofe alhes and grit,” may per- 
haps unite with me in opinion, with Mr. Whitehurst, 

that the crater from whence that melted matter flowed, to- 
“ gether with an immenfe trad of land towards the north, 

“ have 


fome Strata in Ireland and Scotland. * 99 

h have been abfolutely funk and fwallowed into the earth, at 
4C fome remote period of time, and became the bottom of the 
“ Atlantic Ocean. A period indeed much beyond the reach of 
44 any hiftorical monument, or even of tradition itfelf.” 

That you may more readily compare the fpecific gravities of 
the llay lavas, and other fubftances (mentioned in thefe letters) 
with thofe from other parts, I have annexed a table of their 
feveral weights ; and remain, &c. 



A . 

MILLS. 

Ardlun Coal, - 


- I ? 284 

Jet, according to Dr. Watson, 

•as 

1,236 



• l,l80 

Cannel coal, from Haig in Lancafhire, 

*>275 

Whyn Dyke, from near McArthur’s 

head, N° 1 

. 2,863 

Whyn Dyke from Freeport, infide 

N° 2. 

2,88 1 

outfide 

3- 

2,850 

Whyn Dyke from Gartnefs, N° 4. 

m 

2,631 

5- 

- 

2,698 

6. 

- 

- 2,484 

7* 

■1 

2,542 

a. 

«p 

2,322 

9- 

•» 

1 

bi 

V* 

00 

Co 

10. 

m 

2,652 

Bafaltes from the Giant’s Caufeway, 

ate 

2,743 

from Fairhead, 

tsa 

* 2,950 

— from Ardlun, 

m ®a 

2,724 

— from Staffa, 

* « 

2,736 

O 2 


Vitrefcent 


IOO 


Mr. Mills’s Obfervations , &c # 

Vitrefcent fubftance from Ardlun, - - 2 5 8oa 

Toadftone, from great rocks Derbyfliire, yellow grey, 2,133 

dark compadt, 2,634 
ditto cellular, 2,528 

■ yellow grey from Bonfal, 2,219 

i - j 

[Specimens of all thefe fubftances, except the Jet and Cannel 
Coal, accompanied the Paper.] 

EXPLANATION OF THE FIGURES, TAB. IV. 

Fig. l. View of the Glen near Ardlun Head in Mull. 

2. View of the infulated Rock at the termination of the 

Glen. 

3. A view of the great Fiflure, the Cave, and the lufi* 

pended Stones, in the Ifland of Mull. The fiflure 
ranges N. and S., is about ten feet wide and forty 
yards deep : the fides and the fufpended {tones are 
granite. 





[ l°I J 


X. On the Height of the luminous Arch which was feen on Feb. 
23, 1784. By Henry Cavendifh, Efq. F. R . S. and A.S . 

Read February 25, 1790. 

T HIS arch was obferved, at the fame time, at Cambridge 
by Mr. Wollaston ; at Kimbolton in Huntingdon- 
{hire, by the Rev. Mr. Hutchinson ; and at Blockley near 
Campden in Gloucefterfhire, by Mr. Franklin ; and is de- 
ferred in letters from thofe gentlemen read to the Royal 
Society in December 1786 *. 

It has been remarked, that as the arches of the kind de- 
feribed in thefe Papers have ufually but a very (low motion, 
their height above the furface of the earth may readily be 
determined, provided they are obfervecl about the fame time, 
at places fufficiently diftant ; and they feem to be the only 
meteors of the aurora kind whofe height we have any means 
of afeertaining. 

The three places at which this phenomenon was feen are 
not fo well fuited for this purpofe as might at firft be expe&ed 
from their diftance, becaufe they lie too much in the direction 
of the arch ; they however feem fufficient to determine its 
height within certain limits, and perhaps are as well adapted 
for it as any obfervations we are likely to have of fuch phe- 
nomena. * 

The latitude of Cambridge is 52 0 i 2 / 36" : that of Kim- 
bolton is faid by Mr. Hutchinson to be 52 0 20', and, 

* See p. A',— >4.6. of this Volume. 

2 according; 


; 


102 


Mr. Cavendish's Obfervatwns 

according to the fumy of Huntingdonfhire, published by 
Jefferies, is 5 2° 19' 50 " ; fo that we may fuppofe it to be 
feven geographical miles north of Camoudge, and by the maps 
it feems to be about 18 fuch miles weft of it : and Blockley is 
by the map 1 2 geographical miles fouth and 72 weft of 
Cambridge. 

At Cambridge the obiervations ot its track fee in to hate 
been made at about 9 h. I5 / P.M. or 8 h. fdeieal time. 
At Kimbolton, allowing for trie difference of meiidians, 
they could hardly have been made more than § fooner ; and 
at Blockley they were moft likely made nearly at the faznv 
time as at Cambridge. 

At Blockley the arch palled about y° iouth of tire zenith , 
but it is unneceflary to determine this point with precifion. 
At Kimbolton it was found by a quadrant to pafs n 3 to the 
fouth of it ; and at Cambridge it was obferved to pafs through 
2 and e Tauri, /3 Aurigae, 6 Urfae majoris, Cor Caroii, and 
Ardlurus. Now, if an arch was drawn through thefe ftars, 
it muft, I think, have appeared fenfibly waved to the eye; 
whereas Mr. Wollaston did not take notice of any crooked- 
nefs in this part of its courfe. It is moft likely, therefore, 
that the middle of the arch muft have paffed to the fouth of 
/3 Aurigae, and to the north of 6 Urfas; and if a circle is 
drawn through S Tauri, Arflurus, and a point one degree 
north of the zenith, it will differ but little from a great circle, 
will agree as well with thepofitions of thefe ftarsas any regular 
line which can be drawn, and will pafs 2| degrees below (l 
Aurigae, and as much above fiUrfae ; which is not a greater 
difference from obfervation than may well have taken place, 
' confidering how much care and acquaintance with the fixed 
ftars are required to determine a path by them fo nearly. 

7 


The 


on a luminous Arch . 103 

The direction of the arch here defcribed in that part near 
the zenith is W. 1 8° S. ; and if a line is drawn through Cam- 
bridge in this diredion, Kimbolton is 12,8 geographical miles 
north of it; and therefore, as the arch appeared 12 0 more 
fouth at Kimbolton than at Cambridge, the height of the arch 
above the furface of the earth muft be 6i| geographical or 71 
flatute miles. If we fuppofe that the middle of the arch really 
pafied through £ Aurigae, the height comes out 52 ftatute 
miles. On the whole, 1 fhould think, the height could hardly 
be lefs than 52 miles, and is not likely to have much exceeded 

7 I# 

The common aurora borealis has been fuppofed, with great 
reafon, to confift of parallel ftreams of light (hooting upwards, 
which, by the laws of perfpedive, appear to converge towards 
a point; and when any of thefe ftreams are over our heads, 
they appear adually to come to a point, and form a corona. 
Hence, from analogy, it feems not unlikely, that thefe lumi- 
nous arches may confift of parallel ftreams of light, difpofed 
fo as to form a long thin band, pretty broad in its upright di- 
redion, and ftretchedout horizontally to a great length one way, 
but thin in the oppofite diredion. If this is the cafe, they will 
appear narrow and well defined to an obferver placed in the 
plane of the band ; but to one placed at a little diftance from 
it, they will appear broader, fainter, and lefs well defined ; 
and when the obferver is removed to a great diftance from the 
plane, they will vanifh, or appear only as an obicure ill-defined 
light in the iky. 

There are tw r o circumftances which rather confirm this con* 
jedure : firft, that though we have an account of another 
arch befides this * having been feen at great diftances in the 
* That of Feb. 15, 1750. Phil. Tranf. XLVI. p. 47 ^» and 647. 

diredion 


1 04 Mr. Cavendishes Obfervations 

dire 6I1011 of the arch, we have none of any having been feen 
in places much diftant from each other in the contrary dire&ion ; 
and, fecondly, that moft of them have pafled near the zenith, 
whereas otherwife they ought frequently to appear in other 
lituations ; for if they appeared near the zenith to an obferver 
in one latitude, they fhould appear in a very different fituation 
in a latitude much different from that. 

I wifh it to be underftood, however, that I do not offer this 
as a theory of which I am convinced ; but only as an hypo- 
thecs which has fome probability in it, in hopes that by encou- 
raging people to attend to thefe arches, it may in time appear 
whether it is true or not. If it fhould hereafter be found, that 
thefe arches are never feen at places much diftant from each 
other in a diredtion perpendicular to the arch, it would amount 
almoft to a proof of the truth of the hypothefis ; but if they 
ever are feen at the fame time at fuch places, it would fhew 
that the hypothefis is not true. 

Suppofing the hypothefis to be well founded, the height 
above determined will anfwer to the middle part of the band, 
provided the breadth of it was fmall in refpedl of its diftance 
from the earth, but otherwife will be confiderably below the 
middle. If the breadth of the band was equal to th^ diftance 
of its lower edge from the earth, the height of the lower edge 
would be three- fourths of that above found ; and if the breadth 
was many times greater, would be half of it. 

In the common aurora borealis, an arch is frequently feen low 
down in the northern part of the lky 5 forming part of a fmall 
circle. What this is owing to, I cannot pretend to fry ; but it is 
likely that it proceeds from ftreams of light which appear more 
condenled when feen in that direction than in any other, and eon- 
fequently that the ftreams which form the arch to an obferver 


m 


on a luminous Arch. 105 

in one place are different from thofe which form it to one at a 
diftant place, and confequently that no conclufion as to its 
height can be drawn from obfervations of it in different places. 
Attempts, however, have been made to determine the height 
of the aurora from fuch obfervations, and even from thofe of 
the Corona*; though the latter method muff; fu rely be per- 
fectly fallacious, and moft likely the former is fo too. 

Bergman. Opufc. Vol. V. 



Vol. LXXX. 


P 


[ io6 J 


) 


XL Obfervations on Refpiration . 

By the Rev . Jofeph Prieftley, LL.D . F. i?. £ 

Read February 25, 1790. 

W HEN I wrote the Obfervations on the Subject of Re- 
fpiration , publiffied in the Philofophical Tran factions, 
VoL LXVI. p. 226, I fuppofed, that in this animal proceis 
there was limply an emiffion of phlogifton from the lungs. 
But the refult of my late experiments on the mutual tranfmif- 
fion of dephlogifticated air and of inflammable and nitrous air, 
through a moift bladder interpofed between them, and likewife 
the opinions and obfervations of others, foon convinced me, 
that, befides the emiffion of phlogifton from the blood, de- 
phlogifticated air, or the acidifying principle of it, is at the fame 
time received into the blood. Still, however, there remained 
a doubt how much of the dephlogifticated air which we inhale 
enters the blood, becaufe part of it is employed in forming the 
fixed air, which is the produce of refpiration, by its uniting 
with the phlogifton difcharged from the blood : for fuch I take 
it for granted is the origin of that fixed air, fince it is formed 
by the combination of the fame principles in other, but exactly 
fimilar, circumftances. 

Dr. Goodwyn’s very ingenious obfervations prove, that de- 
phlogifticated air is confumed , as he properly terms it, in refpira- 
tion ; but, for any thing that he has noted, it may be wholly 

employed 


Dr. Priestley’s Obfervations, See. \oy 

employed in forming the fixed air above mentioned* He has 
proved, indeed, that the application of dephlogifticated air to 
the outfide of a vein will change the colour of the blood con* 
tained in it. But this might have been effedted, as I firft fup- 
pofed, by the fimple difeharge of phlogifton from the blood, 
when it had an opportunity of uniting with the dephlogifti- 
cated air thus prefented to it. He does not, however, feem to 
fuppofe, that there is any phlogifton difeharged from the blood 
in the a<ft of refpiration, but only that dephlogifticated air 
enters into it. But that my former fuppofition, as well as his. 
is true, will appear, I prefume, from the experiments which I 
lhall prefently recite. 

As, in order to determine what proportion of the dephlo- 
gifticated air deftroyed by refpiration is employed in forming 
the fixed air which is the produce of it, it was neceffary to 
afeertain as exactly as pofiible the proportion of dephlogifticated 
air and of phlogifton in the compofition of fixed air, I repeated 
with particular care experiments fimilar to thofe which I had 
formerly made for that purpofe. 

I heated charcoal of copper in 41 ounce meafures of dephlo- 
gifticated air of the ftandard of 0.33, till it was reduced by wafti- 
ing in water to 8 oz. m. of the ftandard of 1.33. Again ? I heated 
charcoal of copper in 40.5 oz. m. of dephlogifticated air of the 
ftandard of 0.34 till it was reduced to 6 oz. m. of the ftan- 
dard of 1.76. And in each of thefe cafes there was a lofs of 
6 gr. of the charcoal of copper ; fo that there cannot be more 
than 6 gr. of phlogifton in 33 oz. m. of fixed air, and confe- 
quently that only a very little more than one-fourth of the 
weight of fixed air is phlogifton. 

I heated perfectly well burned charcoal of wood in 60 oz. 

of common air, and found one-fifth of the remainder to 

P 2 be 


3 g.8 Dr. Priestley’s Obfervations 

be fixed air, and the refiduum of the ftandard of 1.7. Laftly* 
I heated 8 J gr. of perfect charcoal in 70 oz. m. of dephlogifti* 
cated air, of the ftandard of 0,46, when it ftill continued 70 
oz, m* ; but after wafhing in water it was reduced to 40 oz. 
m. of the ftandard of 0.6, and the charcoal then weighed i£ 
gr. ; fo that from this experiment with common charcoal, as 
well as from the preceding with charcoal of copper, it appears, 
that about one-fourth of the weight of fixed air is phlogifton, and 
confequently that the other three-fourths are dephlogifticated 
air. 

Having done this, I proceeded to afcertain how much fixed 
air was adlually formed by breathing a given quantity both of 
atmofpherical and of dephlogifticated air, in order to determine 
whether any part of it remained to enter the blood, after 
forming this fixed air. 

For this purpofe I breathed in 100 oz. m. of atmofpherical 
air, of the ftandard of 1.02, till it was reduced to 71 oz. nn 
and by wafhing in water to 65 oz. m. of the ftandard of 1.45. 
When the computations are properly made, as directed in a 
former Paper, it will appear, that, before the procefs, this air 
contained 67.40Z. m. of phlogifticated air, and 32.60Z. m.of de- 
phlogifticated air; that after the procefs there remained 53.10 5 
oz. m. of phlogifticated air r and 11.895 oz. m. of dephlogifti- 
cated air ; and that there were only 6 oz. no. of fixed air pro- 
duced ; for the quantity abforbed during the procefs could only 
have been very inconfiderable. It will therefore be evident, that ? 
in this experiment, 20.7 oz. m. of dephlogifticated air, which 
would weigh 12.42 gr. difappeared ; whereas all the fixed air 
that was found would only have weighed 4.4 gr., and one- 
fourth of this being phlogifton, the dephlogifticated air that 
entered into it would have weighed only 3.3 gr. ; confequently 

9.12 


on Refpiration. 109 

9.12 gr. of it muft have entered the blood, which is three 
times as much as that which did not enter, but was employed 
in forming the fixed air in the lungs. 

I breathed in 100 oz. m. of dephlogifticated air, of the 
ftandard of 1.0, till it was reduced to 58 oz. m , and by wafh- 
ing in water to 52 oz. m. of the ftandard of 1.75, with two 
equal quantities of nitrous air. The computations being made 
as before, it will appear, that, before this procefs, this air con- 
tained 66 oz. m. of phlogifticated, and 34 oz. m. of dephlo- 
gifticated air; and that after the procefs there were 30.368 oz. 
m. of phlogifticated air, and 21.632 oz. m. of dephlogifticated 
air. In this cafe, therefore, the dephlogifticated air that difap- 
peared was 13.3 oz. m. weighing 7.8 gr. and the fixed air was 
6 oz. m. weighing 4.4 gr. ; fo that here alfo about three time« 
as much entered the blood as did not. 

Thefe experiments I repeated many times, and though not 
with the fame, yet always with fimilar, refults, the greateft 
part of the dephlogifticated air, but never the whole, pafting 
the membrane of the lungs, and entering the blood. 

When the refults above mentioned are compared, it will ap- 
pear, though the obfervation efcaped Dr. Goodwyn, that part 
of the phlogifticated air entered the blood, as well as the de- 
phlogifticated air ; or, which is the fame thing, that the de- 
phlogifticated air which was con fume cl was not of the pureft 
kind. This experiment I repeated fo often, and always with 
the fame refult, that I am confident I cannot be miftaken in 
th is conclufion. This fa£t, of which I had no previous expec- 
tation, I firft thought might be accounted for by fuppofing, 
that the two conftituent parts of atmofpherical air, viz. the 
phlogifticated and dephlogifticated air, are not fo loofely mixed 
as has been imagined ; but rather that they have feme principle 


no l)r, Priestley’s Observations, &c. 

of union, fo that, though they may be completely feparated by 
fome chemical proceffes, they are not entirely fo in this ; but that 
the dephlogifticated air, paffing the membrane of the lungs, 
carries along with it fome part of the phlogifticated with which 
it was previoufly combined. But, at the obliging fuggeftion of 
Dr. Blagden, I now think it more probable, that the defici- 
ency of phlogifticated air was owing to the greater proportion 
of it in the lungs after the procefs than before. 

T here will always be fome uncertainty in the refults of the 
long-continued refpiration of any kind of air, as at the laft the 
operation becomes laborious, and the quantity inspired and ex- 
pired is therefore much greater than at the firft. But I was aware 
of this circumftance, and endeavoured to obviate the effects of 
it, by leaving off with my lungs as nearly as I could judge in 
the fame ftate of diftentiou as when I began, which was always 
after a moderate expiration ; fo that two or three ounce mea- 
fures would have made a very fenfible difference, as any perlbn 
will find by adlual trial. 



[ III ] 


XII. An Account of the Trigonometrical Operation, whereby the 
Difance between the Meridians of the Royal Obfervatories of 
Greenwich and Paris has been determined. By Major-general 
William Roy, F. R. S. and A. S. 

Read February 25, 1790* 

I NT RODUCTION. 

T HE trigonometrical operation which becomes the fubjeCt 
of the prefent Paper, had its commencement, as will 
be remembered, in the meafurement of a bafe on Hounflow- 
Heath in 1784, an account of which was given to the Royal 
Society in the following year. 

On the completion of that firft part of the bufinefs, it was 
little expected, that nearly three full years would have elapfed 
before, even in this country, an inftrument could be obtained 
for taking the angles ! 

In the fpring of 1787, there were indeed appearances, that 
Mr. Ramsden would have enabled us to embrace the early 
part of the feafon, by proceeding with the execution of the 
main defign ; and therefore Sir Joseph Banks had opened 
(through the official intercourfe of his Majefty’s Secretary of 
State, the Marquis of Carmarthen, with the Ambaflador 
at the Court of France) a correfpondence with the Academy of 
Sciences, regarding the co-operation expected on their part* 
for connecting the triangles which we were now preparing to 
2 extend 


1 


1 1 2 Gen . Roy’s Account of 

extend along the Englifh coaft, with thofe formerly executed 
on the coaft of France, oppofite to Dover. And Dr. Blag- 
den (who for this purpofe confented to lay afide his intention 
of making a tour through Germany that fummer) had engaged 
to affifl in the bufinefs, on the appointment of the Royal So- 
ciety, whenever we fhould be enabled to affign any probable 
time, for the different parties to repair to their refpeftive coafts, 
for the aforefaid co-operation. * 

About the fame time likewife, a Paper was laid before the 
Royal Society, intended as a fketch of the mode propofed to 
be followed in carrying the fcheme into execution ; for which 
purpofe it was accompanied with a general map, filewing 
nearly the difpofition of the triangles, and containing alfo va- 
rious inveftigations concerning the figure of the earth, whereon, 
it is hoped, the refult of the prefent operation will throw fome 
additional light. 

. For feveral months of the fpring and fummer of 17S7, Mr. 
Ramsden had been ferioufly at work in endeavouring to finifii 
the inftrument. Not having employed a fufficient number of 
workmen upon it at the outfet, it was now evident, that he 
had even deceived himfelf, by leaving too much to be done at 
the latter end. At length, however, the inftrument was pro- 
duced, and placed on the 31ft of July at the ftation near 
Hampton Poor-houfe, on the very fpot where, about thirty- 
five months before, the meafurement of the bafe had been 
compleated. 

By commencing an operation of this nature, at fo advanced 
a feafon of the year, it was fufficiently obvious, that only very 
faint hopes could be entertained of bringing it to a conclufion 
before the bad weather would fet in. But it being of much 
importance to get the triangles, which extend acrofs the 
3 Channel, 


the Trigonometrical Operation. i j n 

Channel, at all events executed, it was therefore propofed to 
Comte de Ca ssini, who by this time had been appointed by the 
Academy of Sciences to fuperintend their part of the bufinefs, 
that he fhould fix the time that might fuit him beft for our 
meeting on the coaft ; that we would then difcontinue the ope- 
ration to the weftward, and, having in concert executed the 
coaft triangles, we would refume the inland parts of our own 
feries at fome more convenient opportunity. 

This propofition being readily acceded to by Comte be 
Cassini, the 20th of September was appointed for our re- 
pairing to the coafts of Dover and Calais refpe&ively. 

In the mean time our operation was continued* with all ima- 
ginable care and affiduity, through the firft ten ftations of 
the feries of triangles from Hampton Poor-houfe to that at 
Wrotham Hill inclufively. 

The inftrument, and the various parts of the apparatus* 
were then removed to Dover, at which place MeiT. be Cassini, 
Mechain, and le Gendre, three diftinguifhed Members of 
the Academy of Sciences, arrived on the 23d of September. 

In the courfe of two days that thefe Gentlemen honoured us 
with their company at Dover (and we regretted exceedingly 
that the latenefs of the feafon did not admit of our enjoying 
that pleafure for a much longer period) every thing was fettled 
in the mo ft amicable manner poffible, with regard to the times 
of reciprocal obfervation. 

A great number of white lights, fitted for long diftances, 
and feveral reverberatory lamps had been previoufly provided.' 
Having been fupplied with fuch a proportion of the lights as 
feemed neceffary for their fide of the channel, and one of the 
lamps, the French Gentlemen departed for Calais on the 25th, 
accompanied by Dr. Blagden, who attended them during the 
Vol. LXXX. Q time 


i 14 Gen . Roy’s Account of 

time of the co-operation, until it was finally clofed on the 17th 
of October. 

For the greater part of the time, the weather was extremely 
bad; neverthelefs, on the particular nights when the moll im- 
portant obfervations on our fide were made, namely, thofe at 
Dover and Fairlight Down, the nights happened very fortu- 
nately to be favourable, fo as to enable us to interfedt, with 
great accuracy, the two diftant points on the French coaft of 
B lancnez, and Mantlambert *, and thereby to eftablifh for ever, 
the triangular connection between the two countries. 

The Duke of Richmond, Matter General of his Majefty’s- 
Ordnance, had, in the mod liberal manner pofiible, given 
every affiftance to the operation (from that great department 
over which he prefides with fo much honour to himfelf and 
advantage to the publick) by furnifhing an officer and a de- 
tachment of artillery-men for the work ; ordering the laboratory 
at Woolwich + to fupply whatever fire-works might be wanted 
for fignals ; and temporary fcaffolds to be eredled at Greenwich 
Obfervatory, Shooter’s Hill, and Dover Cattle, for the reception 
of the inftrument. But what was ttill of more importance than 
anv of thefe, his Grace had permitted Lieut. Fiddes. (one of the 
engineers on the furvey then under my direction) to be em- 
ployed, in the lummers of 1786 and 1787, in making a very 
accurate plan of that part of Romney Marfh where the bale 
of verification was to be meafured. In a country lo much in- 
terfered by ditches, and where there were io many ponds of 
water to he avoided, without fuch a plan railed before-hand, 

* The name of this hill is vulgarly pronounced Bouhmberg , and it is even 
written in the lame manner in the book, La Mtridiennc verifies . 

•j* Major Congreve, of the Royal Artillery, had the management of the lights 
at Shooter’s Hill ; and his ailiilance was found to be moil eflentially ufeful. 


the Trigonometrical Operation. l r , 

an operation of fo delicate and difficult a nature could not have 
been effected. 

The apparatus for the meafurement of the bafe with the flee l 
chain, notwithftanding the urgency of the cafe, was not lent 
to its deftinafion until tne end of the firft week of October. To 
Lieut. Fiddss the engineer, was then joined Lieut. Brycs of 
the Royal Artillery; and it was not before' the beginning of 
December, that thefe two gentlemen, with the molt unremit- 
ting labour and perfeverance, were able to accomplifn the mea- 
furement, as will be feen in the detailed account of that ope- 
ration given in the firft fedlion of this Paper. 

In finilhing the co-operation with the French Commiffioners, 
at Lydd on the 17th of October, our inftrument had now 
pafled through fixteen ftations out of twenty-three. There of 
courfe remained yet feven Rations where it was to be placed, 
and obfervations to be made. Eagerly wilhing to bring the bull- 
nefs to a conclufion, we ftruggled on through five of the feven. 
But the weather at length became fo tempeftuous, that it was 
utterly impolfible to continue it, with any hopes of being able 
to make latistacrory obfervations. Perched on the tops of high 
fteeples, fuch as Lydd and Tenterden, or on heights, fuch as 
Hollingborn Hill, we fufficiently experienced, that operations 
of this foit, where the moft important obfervations could only 
be made at night, by means of the white lights, Ihould never 
be undertaken in the latter feafon. 

On the fecond of November, the inftrument was accord- 
ingly removed from the top of Hollingborn Hill, and fent to 
town, leaving the Rations on Goudhurft and Frant Churches, 

both likewife fituated on eminences, unoccupied until the en- 
fuing feafon. 

Q.2 


The 


! j 6 Gen . Roy’s Account of 

The winter months were employed in calculating the ob- 
fervations that had been made; and from thefe we were 
very well enabled to judge to what a degree of accuracy we had 
arrived in determining the Tides and angles: for Frant and 
Goudhurft, having been interfefted from Botley Hill, Wro- 
tham Hill, and Hollingborn Hill ; Goudhurft having been ob- 
ferved from Tenterden, and Frant having (contrary to our 
expectation) been leen and obferved from Fairlight Down, we 
had thereby the certain means of determining very nearly 
what difference there would be between the meafured and 
computed length of either bafe as given by the other, although 
obfervations had not been made at the two intermediate ftations 
of Goudhurft and Frant. This difference, it was feen, would 
fcarcely amount to one foot, or about Tx 4-o- -o^h. part of the 
whole diftance. In as far, therefore, as the refults of the 
plane triangles were concerned, we might have proceeded with 
the computations, and drawn the confequent conclutions,, 
without hefitation, or any rifk of fenfible error. 

But, befides that it might ftill have been faid that tne in- 
ftrument had not been placed at thefe two ftations, there were 
reafons of a different kind, which rendered it In fome degree 
neceffary to place the inftrument not only at Goudhurft and 
Frant, but alfo at Botley Hill and Folkftone Turnpike, where 
it had formerly flood. 

In 1787, when at the ftation of St. Ann’s Hill, in a very 
high wind, the box containing the axis level was blown from 
the fcaffold, and unluckily broken. Mr. Ramsden replaced it 
with one not fo good as the firft ; and it was with this iecond 
level that the obfervations of the pole ftar had been made at 
Dover Caftle. This caftle, although lofty, and fituated on a 

high chalk cliff, that raifes its northern turret about 466 feet 
„ above 


the \ Trigonometrical Operation . ri j 

above low water at fpring tides, is neverthelefs furrounded oti 
the land fide with eminences, at the diftance of fix or feven 
miles, ftill higher than itfelf. From this circumftance we 
found it impoffible to connect it with the great triangles to the 
weftward, otherwife than by a fhort fide. It was therefore 
fufficiently obvious, that it would be eligible to make obferva- 
tions of the pole ftar for determining the difference of lon- 
gitude, and the convergence of the meridians, at fome other 
intermediate ftations between Greenwich and Dover, from 
whence our longeft fides could be diftinftly feen. For this 
purpofe none Teemed fo proper as Botley Hill, Goudhurft, and 
Folkftone Turnpike. The firft of thefe three is only 171 § feet 
eaftward from the meridian of Greenwich, Goudhurft is about 
23 miles fouth-eaftward from the former, and Folkftone Turn- 
pike, the ftation neareft to Dover, is fo fituated, that from it 
can be feen the end of the bafe of verification at High Nook, 
Fairlight Down, and other diftant ftations. 

With this objedt in view, whereon fo much depended, we 
had again the mortification to be thrown into the latter feafon 
of 1788. 

Befides a better level for the axis of the telefcope, the mi- 
crofcope B wanted to be better fupported. Another fort of 
clamp, alfo an eye-piece, with a diagonal prifm for obferva- 
tions near the zenith, or for thofe of the pole ftar in higho 
latitudes, were neceffary improvements, which might have 
been executed in a fhort fpace of time. With thefe altera-- 
tions the inftrument was at laft returned, but fo late, that it 
could not be placed on Goudhurft Steeple till the 9th of. Au-- 
guft, 1788. 

The obfervations at Goudhurft, Frant, Botley Hill, and 
Folkftone Turnpike, having been finilhed early in September,. 

j ' the 


1 2 -8 Gen. Roy’s Account of 

the inftruraent was brought back to town, in the neighbour- 

hood of which it was employed for three days for the follow- 
ing purpofe, 

^ In 1787, when at the Rations of Hundred Acres, Norwood, 
Greenwich, and Snooter s Hul, we had only been able to de- 
termine, in a fatisfaftory manner, two points within the limits 
of the Capital, namely, St. Paul’s Church and Argyll Street, 
the laft by means of the white lights. Bearings of feme 
others, it is tine, were QDtained ; but, in order that thefe 
might be intei fedted in the bed manner, it became neceflary 

to place the inftrument at one or more Rations to the north- 
ward of the town. 

With the view, therefore, of laying the foundation hereafter 
foi a much more accurate plan of London than could poftibly 
be obtained in any other way, the inftrument was placed, firft, 
at Hornfey Hill, to the eaftward of Highgate ; and, fecondly,’ 
on Primiofe Hill, between London and Hampftead. 

Althougn the weather was rather unfavourable at the time 
of making the obfervations from thefe two new ftations ; and 
that the fmoke conftantly hanging over the town in the latter 
feafon impeded us greatly; neverthelefs, the former bearings 
were interfered, and the fituations of a confiderable number 
or remarkable fteeples within London and its environs, were 
accurately determined, as will more fully appear in treating of 
the fecondary triangles. 

Having thus briefly ftiewn the order with regard to time in 
which the recent operation, through its various fteps, was 
progreffively carried on and compleated, it is proper that I 
fhould mention, that Mr. Dalby, who had been recom- 
mended as an affiftant, has acquitted himfelf throughout the 
wnole perfeflly to my fatisfadlion, as a diligent and accurate 

5 obferver, 


the Trigonofnetrical Operation . * j ^ 

obferver, as well as an able and indefatigable calculator. This 
teftimony, which is juftly due to his merit, joined to the fpe- 
cirfien which he gives of his mathematical abilities in the fifth 
fed lion of this Paper, can fcarcely fail of making him better 
known hereafter; and it is hoped, that he will have opportu- 
nities of exerting his talents, by affifiing in the continuation of 
the future operations that are projected and recommended to 
be carried on in the conciufion of this Memoir- the various 
parts of which are arranged as follows : 

SeH ion Fuji-... 

Defcription of the apparatus made ufe of in the meafure- 
meat of the bafe of verification in Homney Marfh, with the 
hundred-feet Reel chain, in the autumn of 1787, with the refult 
of that operation. Reference to be had to Plate I. and II. and 
alfo to the table containing the general detail of the mea- 
furement. 

Section Second 1 

General defcription of the great infer u merit with which the 
angles in the recent trigonometrical operation were obierved ; 
ihewing alfo its various adjpRments for practice. Reference to- 
be had to Plate III. a general view of the entire machine * 
Plate IV. a plan and two feclfions of it ; Plate V. various parts 
lepiefented on large fcale.s;. and Plate VI. the microfcopes and-’ 
eye- pieces. 

Section Third. 

Defcription of various articles of machinery made ufe of m 
the courfe of the trigonometrical operation, referred to in Plate 
V1L Alio- the dIRinclion of the Rations into two lets'; thole 
ot the fecond fet being referred to in Plate VIII. 


T20 Gen. Roy’s Account of 

Settlor* Fourth . 

Calculation of the feries of triangles extending from Wind- 
for to Dunkirk, whereby the geodetical diftance between the 
meridians of the Royal Obfervatories of Greenwich and Paris 
is determined. Reference to be had to Plate IX. 

Settlor Fifth. 

'On the difference between horizontal angles on a fphere and 
fpheroid. Plate X. 

Settlor Sixth . 

Manner of determining the latitudes of the Rations. Ap- 
plication of the pole ftar obfervations to computations on dif- 
ferent fpheres, and alio on M. Bougurr’s fpheroid, for the 
determination of the difference of longitude. Ultimate refult 
of the trigonometrical operation, whereby the difference of the 
meridians of the Royal Obfervatories of Greenwich and Paris 
Is determined. Plate X. 


Settlor Seventh . 

An account of the obfervations made during the courfe of 
the trigonometrical operation for the determination of terreftriai 
refraction. Plato X. 


Settlor Eighth . 

Secondary triangles, fubdivided into two fets, for the im- 
provement of the maps of the country, and the plan of the 
City of London and its environs. Plate Xf. 


Conclufon , 

Containing Propofitions for extending trigonometrical opera- 
tions over Great Britain. 

SEC- 


i 


the Trigonometrical Operation. 


SECTION FIRST. 

Defcription of the apparatus made ufe of in the meafurement of 
the bafe of verification in Romney Marjh, with the hundred- 
feet feel chain, in the autumn of 1787, with the refill t of that 
operation. Reference to be had to Plates I. and II . ; and alfo 
to t he table cont anting the general detail of the meafurement. 


Article I. Preamble. 

IN the account of the meafurement of the bafe on Houn- 
flow Heath in 1784, which appeared in the Philofophicai 
Tranfafhons oi the fubfequent year, we had occafien to fhew, 
how very accurately diftances might be determined by the fteel 
chain, when applied in the ordinary way on the natural fur- 
face of the ground, if that furface happened to be tolerably 
fmooth, which was the cafe in the inftance alluded to. By the 
comparifon of the meafurement of a length of one thoufand 
feet with the glafs rods, and with the chain when ufed with 
an apparatus adapted to the purpofe, it further appeared, that 
the difference between the refults was fo very fmall as fcarcely 
to be difcernible, fince it would not have exceeded half an inch 
on the whole length of that bafe of 27404.7 feet. 

Having always confidered the experiment on Hounflow 
Heath, juft now mentioned, as pofitive proof of the excel- 
lency of the chain, it had been refolved on to apply it to the 
menfuration of the bafe of verification in Romney Marfh, even 
if no other reafons ■ had exifted to make that choice eligible. 
Vol. LXXX. R Rll , 


122 


Gen . Roy’s Account of 

But befides the danger of having the glafs rods broken, in 
trap {porting to fo great a diftance from London, and, on fuch 
an event happening, the impoffibility of getting them replaced 
with others at the advanced feafon of the year in which we 
were unfortunately thrown with the operation, it was obvious, 
that in a plain of the breadth of fix miles, fo much inter- 
fered with ditches full of water as Romney Marfti in reality 
is, the laying of bridges for the tripod {lands, which mu ft have 
been ufed with the glafs rods, would alone have been a very 
troublefome and tedious operation. 

Art. II. Beech Pojis . 

In the firft place, about thirty pofts made of beech wood, 
three inches in diameter, and of different lengths, from two 
feet three inches to three feet fix, and a few of them ftill longer, 
were provided. They were fhod with iron, and each of them 
carried on its top a caft-iron ferrule, with two dovetails project- 
ing from it ; care being taken in driving them into the ground, 
that the dovetails fhould ftand in or nearly in the direction 
of the bafe, as reprefented by the plan and fe&ion of a lingie 
poft, in the middle part of Plate I. The arrangement of 
twenty- four of thefe pofts may be feen at the top of the faid 
plate, for the meafurement of a portion of the bafe equal to 
one hundred yards, or the length of three chains. Sixteen of 
the pofts reckoning from that which ftands in the center of 
the firft group, to that which ftands in the center of the fe« 
cond, and fo on from right to left, were placed at the diftance 
of twenty feet from each other. The firft is fuppofed to co»in- 
cide with the mouth of the pipe funk into the earth, at the 
eaftern extremity of the bafe, at a place called High Nook 
near Dymchurch ; and every fifth poft from that towards the 

left 


the ’Trigonometrical Operation. 12? 

left marks the end of a chain. The other eight pofts in the 
arrangement, that is to fay, the right and left pofts of each of 
the four groups, are fuppofed to ftand twelve or fifteen inches 
from thole in the center. By referring to the elevation near 
the top, and the plans and feftion in the middle part of Plate 
1 . it will be perceived, that thefe pofts, together with certain 
other iron parts of the apparatus fixed to them, hereafter to be 
defcribed, fupport the ends of the coffering for each chain, 
free and independently of the central pofts, to which laft the 
brafs fcales alone are attached. 

Art. HI. Deal Coffers. 

Fifteen deal coffers, numbeied from one to fifteen, were 
neceffary for the length of three chains, being five to each. 
Six of them, that is to fay, the firft and fifth, the fixth and 
tenth, the eleventh and fifteenth, being the firft and laft of 
each chain, were only nineteen feet four or five inches in length. 
The other nine, being the three in the middle of each chain, 
were of the complete length of twenty feet. Thefe coffers 
perfe&ly refembled in fhape, and nearly in dimenfions, the 
cafes of the glafs rods, being ten inches broad in the middle, 
and uniformly of that depth throughout their whole length. 
But from the middle they became gradually narrower, in a 
curvilinear manner, towards each end, where they were only 
two inches wide. The two cheeks or fides were about half an 
inch thick, and the bottom, which entered into a fhallow 
groove in the middle of the cheeks, was an inch in thicknefs. 
Thus the cheeks being thin, bent and applied eafily to the 
bottom, to which they were firmly nailed, and the whole was 
fortified by fmall blocks of wood fattened at intervals in the 
mfide, fometimes above and fometimes below the bottom. 

R 2 From 


X24 Gen. Roy’s Account of 

From the elevation it will be perceived, that nine or ten inches 
of the under extremities of the cheeks were cut off, fo as to 
permit the bottom itfelf to reft on the irons. This conftruc- 
tion of the coffers was found to anfwer very well, that is to 
lay, they were, confidering their length, not fo heavy as to 
be unmanageable, at the fame time that by their general figure, 
and particularly the depth of the cheeks, they were entirely 
prevented from warping. 

In addition to the fifteen coffers, juft now defcribed, a six- 
teenth, not reprefented in the plate, was afterwards prepared 
at Hythe by Lieut. Fiddes, to be ufed occafionally, when the 
end of one chain, and commencement of another, coincided 
with a deep ditch or one of the fewers full of water, and 
where of courfe it would have been extremely difficult, if not 
impoffible, to have fixed fteadily the group of three pofts in 
the ufual manner. In this coffer^ there was a double or falle 
bottom, with grooves adapted for the purpofe ; and the brafs 
fcale, pulley, &e. were removed from the irons, and placed oil 
this bottom a 

Art. IV. Apparatus of caft iron , &c. for the ends of the Chain . 

By referring to the plate, where the feveral parts of the ap- 
paratus for the extremities of the chain are reprefented in plan* 
and feftion, by a fcale equal to one- fourth of their real dimen- 
lions, it will appear, that the caft-iron pieces were of two dif- 
ferent forms, one long, and the other fliort ; but both applied 
in the fame manner, on the ferrules binding the tops of the 
pofts, as has been already mentioned. Of the long kind there 
were in all fifteen or fixteen, that is to fay, one for each poft 
in a length of three chains. Each iron had two clamps on its 
c under 


the 'Trigonometrical Operation. j 2 j 

under fide, which being fiackened, it was placed on its ferrule 
at right angles to the line of meafurement; and being turned 
round 90% the dovetails of the ferrule, Handing originally in 
the dire&ion of the bafe, came within the clamps, which were 
then tightened by four fcrews, turned with fquare keys adapted 
to the purpofe. 

It is fufficiently obvious, that fo many irons, with fuch a 
number of fcrews to each, could not fail of rendering this 
operation tedious ! The bufinefs would have been greatly expe- 
dited if there had been only two fuch fcrews, one on each end 
in a middle fituation ; and, inftead of the four fcrews, there 
Ihould have been four Heady pins, entering eaiily into holes 
prepared for them in the under fide. A fhort groove, of two 
or three inches in length, in each extremity of the bottom, 
would, 011 this fuppofition, have been neceflary to fuffer the 
fquare heads of the fcrews to pafs ; and it will be readily con- 
ceived, that the thicknefs of the bottom would have effectually 
fecured the chain from touching them, prevented the mutila- 
tion of its handles, and faved much lofs of time. Indeed the 
fame purpofe might have been effeded, but not fo advantage- 
oufly, by laying the original four fcrews lower in the iron, 
which its thicknefs eafily admitted off Finally, in order to 
avoid fuch like inconveniencies in future, there is ftill one im- 
perfection more, which it is incumbent on me to remark, 
namely, that cafl-iron ferrules will not anfwer ; for the force 
that was found to be neceflary to drive the polls into the 
ground, burft almoft the whole of them, fo that before the 
operation was compleated, they were obliged to be replaced 
with others made of hammered iron, forged for the purpofe. 

Of the fliort irons only three were neceflary, one for each 
end of the chain, and a fpare one in cafe of accident. They 


were 


12’6 Gen. Roy’s Account of 

were placed, turned, and clamped on the ferrules, In all re- 
fpefts fimiiarly with thofe of the long kind. By infpedtion of 
the plate it will be feen, that each of them carried on its fur- 
face a brafs fcale of fix inches in length, divided into inches and 
quarters, and moveable in a Aide, either backwards or for- 
wards, by a finger- fcrew adapted to the right-hand end. 

The right-hand poft of each group is called the drawing - 
pof, becaufe the iron fixed on its top carries a fmail apparatus 
of brafs, which being connected with the flat iron rod and 
hooks formerly ufed at Hounflow Heath, for a like purpofe, 
lays hold of the rear handle of the chain, and draws it back 
until zero co-incides with the point of commencement. The 
left-hand poft in each group is called the weight -poji, becaufe 
it carried a brafs pulley, over which a weight of 28 lbs. was 
hung by a fmail rope attached to the hooks that laid hold of 
the front handle of the chain. This weight acting againft 
the force of the fcrew at the other end, the chain was thereby 
kept perfectly ftraight in the coffers, and conftantly in the fame 
degree of tenfion, until fome certain divifion (the neareft for 
inftance) of the fcale could be brought, by means of the fcrew, 
accurately to coincide with 100 feet at the front end. That 
divifion, whatever it might be, was of courfe regiftered in the 
field book of the operation, together with the true temperature 
of the chain, as (hewn by five thermometers, one being laid 
for that purpofe in each coffer, and fecured with white cloth 
from the fun’s rays, as cccafion might require. 

Fifteen coffers were always arranged on the ground at the 
fame time, comprehending a fpace of the bafe equal to the 
length of three chains or 100 yards. The extremities of the 
firft chain having been accurately transferred, in the manner 
above mentioned, to the brafs fcales on the tops of the central 
2 pofts, 


the Trigonometrical Operation . j 2 j 

polls, and thefe remaining firm and motionlefs, as being 
wholly unconnected with any other parts of the apparatus, 
the chain was then moved forward into the fecond fet of cof- 
fers, where the thermometers were alfo placed. In thfe mean 
time, the firft fet of coffers now vacated, with their polls, &c. 
were carried on and arranged in the front, for the meafure- 
ment of the fecond ioo feet; and fo on continually with the 
others in fucceffion. 

Art. V. Of the furvey of Romney Marfh previoujly to the 

meafurement of the Bafe. 

In the introduction to this Paper it has been mentioned, that 
the Duke of Richmond had permitted Lieut. Fiddes, of 
the Royal Engineers, to be employed in 1786 and 1787 in 
railing a plan of that part of the Marfh where, on examina- 
tion, it fhould be found, that the bafe of verification might 
be the beft executed. In juftice to that officer, I confider it as 
incumbent on me to fay, that it was impoffible for any perfon 
to fulfil the duties entrufted to him better than he did, either 
in the courfe of the furvey, or fubfequent meafurement of the 
bafe, whereof he alfo had the direction. The general inftruc- 
tions given to him were, that after having by a bafe of his 
own determined certain triangles in the neighbourhood of 
Dymchurch,. Ruckinge, and Romney, by way of foundation 
for his work, he fhould preferve Ruckinge as the point whereon 
the allignement of the great bafe was to be directed, and vary 
the pofition of that end next the fea-wall in fuch a manner as 
to meet with the feweft local ofaftru&ions to the meafurement: 
between the two extremities. By infpedtion of the plan Plate 
II. which comprehends a traft of country of two miles in 
breadth, one on each fide of the bafe line, it will be perceived, 

that 


l2 g Gen. Roy’s Account of 

that befides the numberlefs ditches with which this finguiar 
plain is interfered, and which it was impoffible to avoid crof- 
fing* there is almoft in every field a watering pond for the 
cattle, many of them of confiderable depth. Neverthelefs, fo 
very attentive had Mr. Fiddes been to the accuracy of his 
furvey, that he was enabled, after feveral trials of other di- 
rections, to run a line from High Nook on Dymchurch Sea- 
wall, upon the fmall fpire of Ruckinge Church, of the length 
of nearly fix miles, without interfering with any one of the 
watering ponds, or meeting with any other local obftruetion of 
confequence. So very minute was he in his remarks, and fo 
accurate in the fituation of particular trees, that in tracing his 
line with the telefcope, he managed fo as to avoid them all, a 
few infignificant bufhes excepted ; which I believe to be an 
Inflance of exa&nefs fcarcely to be equalled. 


Art. VI. Pipes funk in the ground . 

Permiflion having previoufly been obtained from the pro- 
prietors of the foil, pipes were funk into the ground at the 
two extremities of the bafe, and alfo one on Allington Knoll, 
which laft point with Lydd Church * form that fide of one 
of the great triangles depending on the bafe on Hounflow 


* It will be perceived, that feveral of the names of places differ m their 
orthography, from that whereby they were expreffed in the plan of the intended 
triangles given in the Paper of 1787. This has been done, on procuring better 
information in that refped than had, formerly been obtained. Mr. Cobb, of 
Lydd, an ingenious gentleman, well acquainted with Romney Marfti, was fo 
obliging as to p.refent me with a manufcript map of that finguiar plain, com- 
piled by himfelf from aftual furveys, where the names and boundaries of the 
waterings , and many other curious particulars, are very diftinitly expelled. 
Our plan of the bafe has therefore derived advantage by adhering to iuch 

refpe^table authority. Heath 


the 'Trigonometrical Operation . 1 29 

Heath, to be firft verified by the meafurement of this new 
bafe. Every field is furrounded with a ditch, in cleaning of 
which the earth and mud are continually thrown out on each 
fide, whereby flat dykes are gradually formed 011 either fide. 
That the meafurement might be carried on as nearly as poffible 
in the fame plane, that is to fay, about fifteen or eighteen 
inches above the common furface, therefore, narrow grooves 
were cut in thefe flat dykes, which the different farmers rea- 
dily confented to without murmuring. Here it is to be ob- 
ferved, that there was no occafion for levelling the line, Rom- 
ney Marlh having been formerly covered by the fea, and a 
confiderable part of it, particularly towards the bottom of the 
range of hills that feparate it from the Wealds of Kent, being 
ftill lower than the fea at high water, would again be over- 
flowed by it, if much care and expence were not annually be- 
llowed in fecuring and repairing the dykes, whereby it is pro- 
te &ed. Thus the line of the bafe may be confidered as an 
inclined plane, defcendmg gradually about five feet from the 
mouth of High Nook pipe to within 246 yards of the Ruckinge 
end, where the ground 111 that direaion feems to be the lowefl. 
Thence it rifes comparatively fuddenly, about fifteen feet, to 
the mouth of the pipe fituated in a fmall field immediately 
adjoining to Ruckinge Church-yard. 


Art. VII. Refult of the meafurement. < 

Lieut. Fiddes, in the courfe of his trigonometrical fur- 
vey, and of the different meafurements he had aaually 
made of the line with a common iron chain, which from 
time to time was compared with ftandard rods of deal, had 
determined the total length of the bafe within a few feet 
of the truth, before the ultimate operation began. He 
.had likewife driven into the ground, at the end of every 
Voe. LXXX, S thoufand 


1 30 Gen. Roy’s Account of 

thoufand feet, a ftrong picket, which were numbered i, 2, 3, 
&c. from the pipe at High Nook to the 28th near Ruckinge. 
In all this preparatory part of the bufinefs he had no other 
affiftants than the artillery-men of his furveying party. But 
for the ultimate determination, it being abfolutely necelTary 
that he fhould have the aid of fome perfon in whom he could 
confide for the management of the operation in general, and 
particularly for the adjuftment of the fcale at one end of the 
chain, while he himfelf was adjufting that at the other ; there- 
fore Lieut. Bryce, of the Royal Artillery (now of the Corps 
of Royal Engineers), an attentive officer and excellent ma- 
thematician, was left with him for thofe effential purpofes. 
Thefe two gentlemen began the operation on the 15th of 
October, and, after experiencing many difficulties arifing from 
the badnefs of the weather in that late feafon of the year, and 
the defe&ivenefs of the apparatus, it was only by dint of great 
labour, and the utmoft perfeverance, that they were enabled to 
accomplifh the meafurement on the 4th of December fol- 
© 

The annexed general table of the bafe, which contains five 
columns, fhews the progrefs that was made in the work from 
day to day. The firft column contains the date ; the fecond, 
the fpaces meafured each day, reckoned by hundreds of yards, 
and denoted in the general plan by ftrong dots ; the third 
fhews the temperature of the chain deduced from the mean of 
fifteen thermometers, five for each chain ; the fourth expreffes 
the difference of temperature above or below 62° of Fahren- 
heit ; and the fifth fhews the correction anfwering to that 
difference, additive to the apparent length with the fign + , 
and fubtradive from it with the fign — . 

2 


lowing 


From 


the Trigonometrical Operation . 

' |kv a 'J •" & i. w * it? ■ ' i 

Feet, 

From infpe&ion of the table it will appear, 
that the total apparent length of the bafe, as 
given direaiy by the Reel chain, was 95 1 2 AVA 
yards; which are equal to 28536 

But when the new points, at the diftance of 
twenty-five feet from each other, were laid off 
on the chain in Mr. Ramsden’s Ihop from the 
original points on the great plank of New-Eng- 
land deal, the temperature was 55°, that is, 7 0 
below 62°; wherefore the contraction of the 
chain by i° of Fahrenheit being =0.00763 in. 
this x 7 0 x 285.37 chains = 1 5.242 in. is the 
reduction for the total contraction below 62°, 
to be taken from the apparent length ; which are 

equal to * " 30 1 

The apparent length is likewife to be leflened 

by the excefs of the corrections with the fign — 
above thofe with the fign + in the annexed table | 
becaufe the temperature of the chain, when ac- 
tually applied to the meafurement, being fo much 
below 62°, the apparent length became thereby 
too great by 30.65 inches, which are equal to 2 

To be deduced alfo from the apparent length, 
the reduction on two hypothenufal diftances, 
meafured at the Ruckinge extremity of the bafe, 
which is fuddenly elevated above the lowed part 
fifteen feet, amounting to 0 

The fum of thefe three reductions, to be taken 
from the apparent length, amounts to - 4 

S 2 


131 

In. Pts. 


8-835 


3.242 


6.6s 


3.023 


0.915 

And 


ij2 Gen. Roy’s Account of 

Feet. In. Pts. 

And confequently there remains for the 
length - - - - 28532 ♦ 7.92 

But when the chain was adjufted in Mr. 

Ramsden’s fhop, as above-mentioned, the tem- 
perature was 55 0 . Being then carried into St. 

James’s Church-yard, its length was laid off on 
brafs pins inferted into the Hone coping of the 
church-yard wall, for the purpofe of compan- 
ion on any future occafion, at which time the 
temperature had changed to 55°!. After the 
raeafurement in Romney Marfh had beenfinifhed, 
the chain in the temperature of 39% being 
ftretched out on the wall, its length was found 
to fall (hort of the original points on the brafs 
pins T W-o °f an inch. Now, 55°.5 — 39 0 = 1 6°. 5, 
and 1 6°.5 x 0.00763 — 0.126 in.; hence 0.126 
— T y^=io.o23 in. is the fpace which the chain 
had only lengthened during an operation which 
continued above fix weeks ; and one-half of this 
fpace, W&.0.0115 multiplied by 285.37 chains 
13 = 3.282 in., the correction to be added to the 
apparent length for the wear of the chain during 
the operation - 4*0. 3.282 

Whence the length becomes - 28532 • 1 1*202 

Laftly, the bafe is to be Ihortened for its 
height of 15I feet above the mean level of the 
fea, fuppofed to be 6 feet 8 inches above low- 
water ipring tides at High Nook, which gives 
for the reduction - - - — o. 0.166 


And 


the Trigonometrical Operation . 133 

Feet. In. Pts. 

And hence there remains for the ultimate or 
true length of the bafe of verification, in the 
temperature of 62° of Fahrenheit’s thermo- 
meter, being the heat to which that on Houn- 
flow Heath was reduced, - - 28532.11.036 

Which make 28532,92 feet. 

Art. VIII. Remarks on the comparative accuracy of the two 

bafes . 

With regard to the accuracy of the meafurement of this 
bafe, compared with that executed on Hounflow Heath in 1784, 
from the infinite pains and care bellowed in both operations, 
it is very difficult to fay, to which the preference fhould be 
given. The expanfion of glafs being fo much lefs than that of 
Heel, if manageable glafs rods of equal length with the chain 
could have been obtained ; then, as far as that fingle circum- 
ftance might have affe&ed the refult, a meafurement made with 
fuch glafs rods would undoubtedly have deferved the pre- 
ference to one with the Heel chain. But when it is confidered, 
that the expanfion of Heel was determined by the pyrometer 
with the fame care as that of glafs ; that the wear of the chain 
is fo very fmall, as we have Ihewn it to be, in fix weeks ufe ; 
that coffers were laid for it, and its length transferred by means 
of the brafs fcales to the tops of immovable polls ; that, in the 
prefent cafe, there was but one-fifth part of the error arifing 
from faulty co-incidences as with the twenty-feet glafs rods ; 
■on this view of the matter, the preference feems to be due to 
the meafurement by the Heel chain, fuppofing always the 
error in excefs, caufed by the deviation from the aUignement- 
horizontally or vertically, to have affected both equally. 


As 


134 Gen. Roy’s Account of 

As a proof that the expanfion of the chain was accurately 
determined, I (hall clofe this fe&ion with a remark repeatedly 
made by the two gentlemen entrufted with the execution of 
this laft meafurement. At the clofe of each day’s work, the 
two fcales marking the extremities of the laft chain (after re- 
giftering the divifions of co-incidence) were left upon their 
refpe&ive pofts until the next morning. They were fecured 
during the night, from being difturbed by cattle, with a cer- 
tain number of the fpare pofts driven into the ground around 
them. A tent was alfo pitched between the two, where fome 
men of the party conftantly lay, by way of a guard for the 
whole apparatus. On the recommencement of the operation 
the fubfequent morning, the chain being applied anew to the 
brafs fcales \ if the temperature continued the fame, the co- in- 
cidences were found to be equally accurate as on the preceding 
night ; but if it had changed one or two degrees, the chain 
never failed unequivocally to fhew it, by falling fhort of the 
divifions on the fcales, if the cold had increafed, or by over- 
reaching them if it had diminifhed. 

Finally, with refpedt to the fubje£t of thefe bafes, it is here 
to be remarked, that the bafe of verification in Romney Marfli 
makes with the meridian of the pipe at High Nook an angle 
of 54 0 28 56" | north- weftward; and that bn Hounflow 
Heath makes with the meridian of the pipe at Hampton Poor- 
houfe an angle of 44 0 41 ! 49", alfo north -weftward* 


General 


[To face page 134.] 


General Table of the Meafurement of the Base of Verification in Romney Marsh, executed in the Autumn of 178*7, wherebv theanmr™i-r M ^ • r , 

to be 9 5 i2 T Vo S oV Yards, and the true, or correded Length in the Temperature of 62% 28532^- Feet PP g h 1S ° Und 


Days. 

Spaces 

Temperature. 

Correction 
for the 
difference. 

Days. 

Spaces 

meafured. 

Temperature. 

Corredtion 
for the 
difference. 

Days. 

Spaces 

meafured 

Temperature. 

Correction 
for the 
difference. 

Days. 

Spaces 

Temperature. 

Correction 
for the 
difference. 

Days. 

Spaces 

meafured. 

Yards. 

Temperatuie. 


Yards. 

Mean by 
1 5 Therm. 

diff. 

from 6z°. 

Yards. 

Mean by 
i5Therm. 

diff. 

from 62°. 

Yards. 

Mean by 
1 5Therm. 

diff. 

from 62°. 

Yards. 

Mean by 
i5Therm 

diff 

frcm 62°. 

Mean by 
1 5 Therm 

diff. 

from 62" 

oa 




In. Parts. 

oa. 




In. Parts. 

Nov. 




In. Parts. 





In. Parts. 






15 

100 

54-7 

- 7-3 

0.167 1° 


2100 

65.0 

+ 3.0 

+ 0.06867 


4100 

55-2 

- 6.8 

0.15565 


6lOO 

42° 1 

-19.9 

0 - 4555 1 


8100 

0 

0 


l6 

200 

62.7 

+ 0.7 

+ 0.01602 


2200 

64.1 

+ 2.1 

+ 0.04807 

10 

4200 

55-3 

- 6.7 

0 -I 5336 

Nov. 

6200 

39-3 

-22.7 

0. 5 iq6o 


8200 


2 5- 7 



3 °° 

61.3 

- 0.7 

0.01602 


23OO 

56.7 

- 5-3 

O.I2I32 


43OO 

53-6 

- 8.4 

0.19228 

21 

63OO 

43-3 

-18.7 

0.42804 

Nov. 

8300 

3 Q. Q 



D 

400 

57 -o 

- 5 -° 

0. 1 1445 

3 ° 

24OO 

58-7 

- 3-3 

0.07554 


44OO 

49 0 

-13.0 

0.29757 


6400 

46-5 

-25.5 

0 - 35*79 

29 

8400 

34.8 

— 27. 2 



5 °° 

52.2 

- 9.8 

0.22432 


2500 

59-5 

- 2.5 

0.05722 

12 

4500 

5 o.i 

-11.9 

0.27239 


65OO 

45-6 

— 16.4 

0 - 3754 ° 


8500 

40. <: 




600 

53 - 6 

- 8.4 

0.19228 

3 1 

2600 

57-3 

- 4-7 

0.10758 


4600 

47-9 

-14. 1 

0.32275 

22 

6600 

42.5 

-19-5 

0.44635 


8600 

42.2 



20 

700 

46.8 

-15.2 

0-34793 


2700 

54-6 

- 7-4 

0.16939 

13 

4700 

44-7 

- 27-3 

0.39600 


6700 

42.2 

- 19.8 

0.45322 

3 ° 

8700 

20. c 

y'l 



800 

58.9 

- 3 - 1 

0.07096 

Nov. 

2800 

53-9 

- 8.1 

0.18541 


4800 

44.8 

—17.2 

0-39371 


6800 

41.2 

-20.8 

0.4761 1 


8800 

44.3 

— 17.7 


23 

900 

53-9 

- 8.1 

0.18541 

I 

29OO 

49 -° 

-13.0 

0.29757 


4900 

4 L 3 

— 20.7 

0.47382 

23 

6900 

39-8 

-22.2 

0.50816 

Dec. 

8900 

46.0 




IOOO 

55-3 

- 6.7 

0.15336 


3000 

54 -° 

- 8.c 

0.18312 

14 

5000 

41.8 

— 20.2 

0.46238 


7000 

39 ° 

-23.0 

0.52647 

I 

9000 

43 -o 

— lq.o 


24 

1 100 

55-7 

- 6.3 

0.1442 I 


3 T0 ° 

5°-9 

— II. I 

0.25408 


51OO 

42.9 

-19.1 

0.43720 


7100 

37-7 

- 24-3 

0.55623 


9IOO 

45 6 

— 16.4. 



1200 

50.0 

— 12.0 

0.27468 

2 

3200 

49.1 

— 12 9 

0.29528 

15 

5200 

45-3 

— 16.7 

0.38226 

24 

7200 

36.2 

-25.8 

0.59056 


9200 

48.7 

— 1 2 . 7 



l 3 °o 

55-2 

- 6.8 

0.15565 


3300 

50-4 

— 1 1.6 

0.26552 


53 00 

44.1 

- 17-9 

0.40973 


73 °° 

42.1 

-19.9 

°- 4555 r 

3 

9300 

41.1 

— 20.0 


26 

1400 

59 -i 

- 2-9 

0.06638 


3400 

48-5 

- J 3-5 

0.30901 


5400 

40.4 

— 21.6 

0.49442 


7400 

40-5 

-21.5 

0.49213 


94OO 

46.9 

— I^. I 



1500 

60.0 

— 2.0 

0.04578 


3500 

42.6 

-19.4 

0.44407 

l 6 

55 00 

4 i -5 

— 2O.5 

0.46924 

26 

75 oo 

35-2 

-26.8 

0.61345 

■4 

9512.2454 

48.4 

— 12.6 


27 

1600 

59 * 

- 2.9 

0.06638 

5 

3600 

52-3 

- 9-7 

0.22203 


5600 

44-8 

— 17.2 

0.39371 


7600 

39-8 

- 22.2 

0.50816 







1700 

63.1 

+ 1.1 

+ 0,02518 


3700 

53 -° 

- 9.0 

0.20601 


5700 

44.6 

-17.4 

0.39829 


7700 

38.5 

-23.5 

0-53791 







1800 

68.1 

+ 6.1 

+ 0.13963 


3800 

52-4 

- 9.6 

0.21974 

17 

5800 

40.6 

— 21.4 

0.48985 

27 

7800 

33-6 

—28.4 

0.65098 







1900 

57-9 

— 4.1 

0.09385 

' 

3900 

47-3 

-14.7 

0.33648 


5900 

39-4 

— 22.6 

°- 5 I 73 I 


7900 

38-9 

-23.1 

0.52876 






2 9 

2000 

60.8 

— 1.2 

0.02747 

7 

4000 

55-6 

- 6.4 

0.14650 


6coo 

41-3 

20.7 

0.47382 

28 

8coo 

32-7 

- 29-3 

0.67068 





- 





-2.16540 





— 3 - 779 1 3 





- 7-58574 





— 10.14802 







Correction 
for the 
difference. 


0-58827 

0.52189 

0.51502 

0.62261 

0 . 4 Q 2 I 2 

O.45093 

O.jalOJ 

O.4O5I5 

O.36624 

O.4349I 

0.37540 

O.30444 

O.4784O 

0 . 345 6 4 

O.34942 


6.97148 
■ IO.I4802 
7-58574 
3- 779*3 
2.16540 


Total Correction — 36.64977 


Feet. In. 

From the above Table it appears, that the total apparent length of the Bafe, as given immediately by the Steel Chain, was 9512^^ yards, which are equal to 28536 8.835 
The correftions in the above Table, and others ipecified in the Text, being fubtra&ed from the apparent length, — — — 3 9.799 

There remains, for the true length of the bafe in the temperature of 62° of Fahrenheit, — — — — 


equal to — 


28532 1 1.036 
28 53 2 tot Feet. 


SECTION 



the 'Trigonometrical Operation. 


*35 


SECTION SECOND. 

General Defer iption of the great infrument with which the angles 
in the recent trigonometrical operation , were obferved ; f dewing 
alfo its various adjufments for practice. Reference to be had to 
Plate III. a general view of the entire machine ; Plate IV. a 
plan and two fedlions ; Plate V. various parts reprefented t® 
large feales ; and Plate VI. the microfcopes and eyepieces*. 


Article I. Preamble . 

IN endeavouring to deferibe the curious instrument made ufe 
of for obferving the angles in the recent trigonometrical ope- 
ration, it has been judged beft to confine ourfelves to the prin- 
cipal parts, without entering into any detail of the minutiae i 
for even to have mentioned thefe,. with the almoft infinite 
number of little ferews that Serve to unite them into one entire 
machine, which could only have been done by references to a 
multitude of great and fmall Roman and Greek characters,, 
would have been a difgufting labour. By the help of the four 
plates which this defeription refers to, and which have been 
executed with great care, that fewer words might Suffice, it is 
hoped, that the inftrument may be underftood by two claffes 
of people for whom it is chiefly intended ; firft, by thofe who* 
being poflefled of fuch a machine would wifli to make them- 
Selves matters of its ufe; and, Secondly,, by fuch ingenious 
artifts as would attempt to conftruCt fuch another; tor thefe 
laft, in particular, the parts that are of brafs, of bell-metal, 

or: 


i^6 Gen. Roy’s Account of 

or of Heel, are diftinguifhed from each other. And here it is 
neceffary to obferve, that the plates muftvnot only be fre- 
quently confulted, but alfo attentively confidered, and repeat- 
edly compared with each other, in the courfe of this de- 
icription. 

Art. II. General view of the in/lrument . 

It is a brafs circle, three feet in diameter, and may be called 
a great theodolet, rendered extremely perfect ; having this ad- 
vantage in particular, which common theodelets have not, that 
its tranfit telefcope can be nicely adjufted by inverfion on its 
fupports ; that is to fay, it can be turned upfide down, in the 
fame manner that tranfit- inftruments are, in fixed obfervatories. 

The circle is attached by ten conical tubes, as fo many radii) 
to a large vertical, conical hollow axis of twenty- four inches 
in height, which may be called the exterior axis. Within the 
bafe of this hollow axis, a collar of call fteel is ftrongly 
driven ; and on its top there is inferred a thick bell-metal 
plate, with Hoping cheeks, which, by means of five fcrews* 
can be raifed or deprefled a little. 

The inftrument refts on three feet, which are firmly united 
to each other at the place where they branch off, by a ftrong 
circular plate of bell-metal, upon which rifes another vertical 
hollow cone, of lefs fize than the former, being included 
within it, and is therefore called the interior axis. On its top 
is inferred a caft-fteel pivot, with Hoping cheeks, paffing 
through the bell-metal plate on the top of the exterior axis, 
the cheeks of the one being nicely ground to fit the cheeks of 
the other. The bell-metal bafe of this interior axis is in like 
manner ground to fit the caft-fteel collar in the bafe of that 
which is without it. Thus the circle being lifted up by two 

men 


the Trigonometrical Operation . igy 

men laying hold of its radii, and the exterior being placed 
upon the interior axis, the cheeks at the top being at the fame 
time adjufted to their proper bearing, it turns round very 
fmoothly, and is perfectly, or at leaft as to fenfe, free from 
any central (hake. This mode of centering is one of the chief 
excellencies of the inftrument. From the ufe that has been 
made of it both years, it fee ms not to have fuffered in the 
leaft; and it is perhaps the only con Fraction that could have 
anfwered for a machine of fuch magnitude, undergoing fo 
many quick tranfitions from place to place, and fo often raifed 
to high fituations without any rifk of being thereby hurt. 

Art. III. Mahogany Planes under the injirument . 

By infpeftion of the plates, but more particularly the IIIcl, 
and the fe&ion towards the right hand in the Vth, it will be 
feen, that there are three planes of mahogany under the metal 
parts of the inftrument ; namely, that which forms the top of 
the ftand, which, although a fquare of about three feet four 
inches at bottom, becomes, by the feparation of the legs, an 
o&agon at top. In the center there is a circular opening of 
nine inches diameter, the ufe of which will appear hereafter. 
Over the top of the ftand lies another plane of mahogany, like- 
wife an oftagon, of fomewhat greater dimenfions than the 
former, with a circular curb running around it, about half an 
inch within the planes of its fides. This o£tagon hath in its 
center an open conical focket of brafs, three inches in diame- 
ter ; and on four of its oppofite fides there are fixed four ftrong 
brafs fcrews, one on each fide, which a&ing againft pieces of 
brafs inlaid into the oppofite fides of the top of the ftand, the 
o&agon plane, with every thing that refts on it, may thereby 
be moved in four oppofite dire£Uons, until the plummet fuf- 
Vol. LXXX. 1 T pended 


j -8 Gen. Roy’s Account of 

pended from the center of the inftrument above, is accurately 
brought to co-incide with the point marking the ftation under- 
neath. The third or uppermoft plane of mahogany is in fa<ft a 
part of the inftrument itfelf, being at all times by fcrews or 
otherwife united to it, and carrying the handles whereby it is 
lifted out for ufe, or in again into its cafe, to be tranfported 
from place to place. In the middle of this plane or bottom to 
the inftrument, there is another conical brafs focket, of three 
inches and a quarter in diameter, fitted to flip over and turn 
eafily on that in the center of the odtagon underneath. In the 
brafs cover of this focket, there is a very fmall hole concentric 
with the inftrument, to fuffer the thread or wire to pafs, which 
fufpends the plummet ; and in the view, Plate III. may be 
feen another fmall box that contains the thread, with a winch- 
handle for railing or lowering the plummet, according as the 
height of the inftrument above the ftation on the ground, or 
edifice where it ftands, may require. 

Art. IV. Feet Screws for levelling the infrument. 

By attending to the group reprefenting the front elevation of 
the feet fcrews, with its fide nuts, in the right hand upward 
angle of Plate V. it will appear, that they are blackened, which 
is always the cafe before the inftrument is levelled, to give 
room for that operation by the adtion of the fcrews. This 
being done, the fide nuts are brought to prefs gently on the 
horizontal plate that embraces the whole group, and thereby 
keeps the inftrument as it were united to the mahogany until 
feme freih adjuftment becomes neceffary. When the inftru- 
ment is to be put into its cafe, then the feet are let down, and 
by the fide nuts the horizontal plate is brought to prefs ftrongly 

on 


the Trigonometrical Operation. 139 

on the whole group, whereby it is kept perfectly fa ft and fe- 
cure from motion in carrying from one fituation to another. 

Art. V. Blocks of box wood and conical rollers under the 

feet fcrews . 

By referring alfo to Plate V. it will appear, that direftly 
below each foot there is fixed to the lower furface of the ma- 
hogany a fmall block of box wood, curvilihear in the direction 
of its motion. On thefe three blocks refts the whole weight 
of the inftrument, which neverthelefs can be moved circularly 
on them alone. But to render the motion perfectly eafy, three 
conical brafs rollers, placed fomewhat nearer to the center, are, 
by means of their refpeftive fprings and regulating fcrews, 
brought to a ft and receive fuch a proportion of the weight as 
it may be neceffary to lay upon them. The head of one of 
thefe fcrews, which give more or lefs aftion to the rollers, may 
be feen at D in the principal view of the inftrument Plate III. 
as well as in the plan and feftion Plate V* 

Art. VI. Screws giving motion to the whole infrument. 

By examining attentively the general view of the inftru- 
ment may be feen, in two politicos, the great fcrew with the 
flat ivory head, whereby the entire machine received a circular 
motion. In one, it is attached to the curbs, as when in ufe in 
1787; in the other, it is laid upon the mahogany bottom, as 
was the cafe the fame year every time it was carrried to a new 
fituation. But this ivory-headed fcrew having been found to 
aft by jerks in moving fo great a weight, and confequeiitiy to 
be troublefome in adjufting the inftrument to the fixed point, 
or that of commencement in meafuring angles ; it was there- 
fore laid afide in 1788, and another apparatus or clamp was 

T 2 adapted 


140 Gen. Roy’s Account of 

adapted for the fame purpofe. This laft may be feen attached 
to the curbs, as reprefented towards the right hand of Plate V. 
It confifts of a brafs cock, fixed to, and projecting outwards 
from, the curb of the inftrument ; which cock is aCted upon 
by two fcrews working on the oppofite tides againft it, and 
which are clamped to the curb of the oCtagon. 

Art. VII. Mahogany Balujlrade and Cover . 

The curb, whereon the three feet of the inftrument reft, 
carries a baluftrade of mahogany fitted to receive, on the top 
thereof, a mahogany cover, no where reprefented except in the 
two feCtions in Plate IV. In this cover there are only four 
imall openings (betides that which allows the great vertical 
axis to pafs), viz . one for each vertical microfcope, one for the 
clamp of the circle, and one for the focket of the Hook’s-joint, 
The two laft are lefs than the former. At the fame time that 
this cover effectually fecures the circle with its cones from dirt 
and from accidents, it ferves conveniently for laying the Hook’s- 
joint upon, or any thing that may be conftantly wanted near 
at hand ; but more particularly for placing the lanterns ufed at 
night for reading off the divifions on the limb of the inftru- 
ment that come immediately under the vertical microfcopes. 

Art. VIII. Achromatic Telefcopes. 

Two achromatic telefcopes, each of thirty-fix inches focal 
length, with double objeCt-glaffes of two inches and a half 
aperture, belong to the inftrument. They are excellent of 
their kind, and are furnifhed with eye-pieces of different mag- 
nifying powers, for ereCt as well as inverted vifion. The lower 
telefcope lies exaCtly under the center of the inftrument, and is 
direfted through one of the openings of the baluftrade. Being 

only 


the 'Trigonometrical Operation . 14 1 

only ufed for terreftrial objects, it requires but a fmall elevation 
or depreflion, and therefore is only fupplied with a fhort axis 
of feventeen inches in length, fupported by braces attached to 
the feet. The eye end of this telefcope is purpofely made hea- 
vier than the objedt end ; and refting on an horizontal arm, 
that is raifed or deprefled by rack-work, it is thereby readily 
brought to bear, and remain very fteadily, upon its -objedt. 
The rack-work may be leen in the view of the inftrument, 
and alfo on the left fide of the right hand fedtion in Plate IV. 
But there is a fmall horizontal motion that can be given to the 
right hand end of the axis of this telefcope, which is effected 
by means of a handle inferted through the vacancy of the ba- 
luftrades, and placed on a dovetail at E, which could not be 
fhewn in the plate. Thus the inftrument being nicely levelled, 
the upper telefcope at zero, and likewife on its objedt, the 
lower telefcope, by the help of this adjuftment, is brought 
accurately to the fame objedt, fuppofed to be the point of com- 
mencement, or that from which angles are meafured. 

By referring to Plates III. and IV. and likewife to the fedtion 
on the left fide of Plate V. it will be feen, that a horizontal 
bar extends acrofs the top of the vertical axis, fupported by 
two fide braces that fpring from the cone, about one-third of 
its height above the plane of the inftrument. The horizontal 
bar carries the Y’s or fupports, in which the pivots of the 
upper telefcope move. They are of fuch height as to permit a 
femicircle of fix inches radius, attached to the axis of the 
tranfit, to pafs freely, and confequently the telefcope to be 
diredted to the fun or ftars in high elevations, but not to be 
brought to the zenith. The arc of excefs of the femicircle 
likewife admits of feveral degrees of depreflion being mea- 
fured thereon. 


Art* 


Gen . PvOy’s Account of 


1 4 % 

Art. IX, Spirit Lev eh. 

The inftrument has two very good fpirit levels, that are 
fitted with the feverai means of adjuftment, as is uiual in fuch 
cafes, the detail of which it is unneceffary here to enter into. 
The firft or axis level, becaufe it is only applied on the axis of 
the telefcope, is that whereby it is fet horizontal, as in the 
ordinary tranfit inftrument ; and it is likewife ufed for placing 
the conical axis truly vertical, fo that the inftrument may turn 
round without fenfible alteration of the level, previoufty to 
obfervations of the pole ftar, or of other heavenly bodies. 

The fecond, or elevation level, is that whereby the telefcope 
is brought to be truly horizontal, when angles of elevation or 
depreffion are to be taken. At fuch times it is fufpended on a 
rod attached to the outfide of the telefcope, to whofe axis of 
viiion the rod, by adjuftment, can be made parallel, as will 
readily be conceived, by obferving the reprefentation of thefe 
parts in the right hand feCtion of Plate IV. 

When the angles of elevation or depreffion to be deter- 
mined are very fmall, they are meafured by the motion of an. 
horizontal wire in the focus of the eye-glafs of the telefcope ; 
but when great, their quantity is meafured by the arc of mo- 
tion of the femicircle, as fhewn by its proper horizontal 
microfcope. 

The elevation level is likewife made ufe of for levelling the 
inftrument when horizontal angles only are to be taken, for 
which purpofe it is fufpended on two pins, which are feen 
projecting from the horizontal bar in the plan, and one of 
them in each of the feClions in Plate IV. This was the ordi- 
nary pofition of the elevation level when the angles of the 
2 triangles 


the trigonometrical Operation * 43 

triangles were obferved, and thereby it was eafily feen in the 
courfe of the operation, whether the inflrument had fuffered 
any change to render a re-adjuftment neceffary. 

Art. X. Lanterns for the Illumination of the IV ires. 

The axis of the tranfit telefcope rs*hollow, and in the middle 
there is placed, at an angle of 45 0 with the axis of vifion, a per- 
forated elliptical illuminator for throwing light on the wires in 
night obfervations. The light is communicated from a fmall 
lantern attached to the horizontal bar at its jundlion with the 
brace, direflly oppofite to the end of the axis, which has a bit of 
thin glafs placed before it to prevent duft from entering. There 
is another fuch lantern for the lower telefcope, not however 
reprefented in the plate. As the light given by thefe lan- 
terns was found to be rather too weak, efpecially that for the 
upper telefcope, therefore it was cuftomary in pradlice to .illu- 
minate the wires, by holding up frontwife one of thofe feen in 
the fedlion in Plate IV. againft the end of the axis of the upper 
telefcope, when directed to the pole ftar. The fame method was 
ufed by prefenting it obliquely to the object-glafs of the lower 
telefcope, when it became neceffary to examine whether the 
interfe£lion of the wires continued without fenfible variation 
on a reverberatory lamp, commonly placed twelve or fifteen 
miles off, and fometimes even at the great diflance of twenty 
or twenty- four miles. 

Art. XI. Lanterns for throwing light on the Divifions of the 

infrument . 

Befides the two fmall lanterns for illuminating the wires of 
the telefcopes in night obfervations, two larger ones may be feen^ 
as already mentioned, {landing on the mahogany cover in the 

fe ci ion 


$44 GV//. Roy’s Account of 

feftion ia Plate IV. ufed for reading off the divifions of the 
inftrument, under the vertical microfcopes. The fron r of one 
of thefe is (hewn, and the back, or that to which the handle 
is fixed, of the other. Their narrow fides are prefented 
towards the microfcopes, there being in each a filvered re- 
flector of copper at FF ; and oppofite to it, at GG, a fcreen of 
talc or tranfparent oiled paper. The light from a wax candle 
being thrown on the reflectors, and thence back again through 
the fcreens, on the divifions of the inftrument under the mi- 
crofcopes, thefe could be very diftinCtly read off and regiftered : 
for the light communicated in this way was very ftrong, at 
the fame time that the glare of it, which otherwife would 
have been difagreeable to the fight, was removed by paffing 
through the fcreen. 

Art. XII. Arms projecting from the bell-metal plate under the 

plane of the infrument. 

By referring to Plates III. and IV. but more particularly the 
latter, it will be perceived, that there are three flat arms, 
fir on gly fixed by fcrews to the edge of the circular bell-metal 

( i 

plate, forming, as has been already mentioned, the bafts of the 
interior vertical axis. Thefe arms, which are alfo firmly braced 
to the feet of the inftrument, rife gradually as they project 
outwards towards the circumference of the circle, whofe radius 
they exceed about an inch and a quarter, and their extremities 
are about an inch lower than its upper furface. One arm, 
lying direCily over one of the feet, is that to which are 
attached the wheels and fcrew moved by the HookVjoint, and 
alfo the clamp of the circle, as reprefented in Plate V. The 
other two arms, whereof one lies alfo over a foot, and the 
other diredliy oppofite to it, become thereby a diameter to the 

circle, 


the ^Trigonometrical Operation. 145 

circle, having their extremities terminated in a kind of blunted 
triangular figure, forming the bafes of pedeftals whereon ftand 
the vertical microfcopes hereafter to be defcribed. The arms, 
together with the horizontal bar and braces carrying the tranfit 
teiefcope, are every where pierced, in order to leflen the weight 
without diminiftung the ftrength of the parts. 

Art. i g, Vertical Microfcopes. 

Two vertical microfcopes, diftinguiftied A and B, are ufed 
for reading off the divifions on the oppofite fides of the circle 
immediately under them. They are exactly of the fame con- 
ftru&ion, and the chief parts of that marked A are reprefented 
in their real dimenfions towards the left hand of Plate VI.; 
where, befide the general, may be feen particular plans of the 
Hides, and alfo that of the pedeftal, containing within it the 
gold tongue, with its axis and fcrews for adjuftment. Next to 
thefe plans ftand the elevation and optical lines, (hewing the 
pofition of the glafies with the magnified fcale at the bottom. 

Each microfcope contains two Hides, one lying immediately 
over the ether, their contiguous furfaces being in the focus of 
the eye-glafles. The uppermoft, or that neareft the eye, is a very 
thin plate of brafs, to the lower furface of which is attached 
the fixed wire, having no other motion than what is neceffary 
for adjuftment, by the left hand ferew to its proper dot, as 
hereafter to be explained. 

The fteel Aide immediately under the former is made of one 
entire piece, of fufficient thicknefs to permit the micrometer 
ferew, of about 72 threads in an inch, to be formed of it. To 
its upper furface is fixed the moveable wire, which changes its 
place by the motion of the micrometer head, feen in the plan 
and elevation towards the right hand. The head is divided 
Vol. LXXX. U m into 


1^6 Gen. Roy’s Account of 

into 60 equal parts, each of which reprefents one fecond of 
angular motion of the telefcope. By examining the particular 
plan of this Reel Aide, it will be feen, that it is attached by a 
chain to the fpring of a watch, coiled up in the ufual manner, 
within a fmall barrel adjacent to it in the frame. By this pro- 
vifion no time whatever is loft; the fmalleft motion of the 
head being inftantly (hewn, by a proportionable motion 
of the wire, to one hand or the other, in the field of the 
microfcope. 

It is necefiary to remark, that the whole microfcope be- 
tween its pillars can be raifed or deprefled a little more or lefs, 
with regard to the plane of the circle, by the help of two fteel 
levers, feen one on each fide of the elevation, which for that 
purpofe are applied in the holes reprefented above and below 
the proje&ing plate that unites the tops of the pillars. By 
means of this motion, diftindtnefs is obtained at the wires ; 
and by the motion of the proper fcrew of the object lens, 
which neceffarily follows that given to the whole microfcope, 
the fcale is fo adjufted as that fifteen revolutions of the head 
fhall move the wire over fifteen minutes, or one grand divifion, 
on the limb, equal to nine hundred feconds, each degree on 
the circle being only divided into four parts. This operation 
being delicate, requires great patience and many repetitions, 
before the purpofe can be exactly, or even nearly, effedted : 
for at the fame time that the fixed wire mu ft bifedt the dot on 
the gold tongue, the moveable wire muft alfo bifedt the dot at 
i8o c on the limb, as well as the firft notch in the magnified 
fcale at the bottom of the plate, where the minutes in the field 
of the microfcope are reprefented in the proportion of between 
fifteen and fixteen to one as painted on the eye of the obferver. 
In this adjuftment there is yet another circumftance to be 
5 attended 


the 'Trigonometrical Operation* 147 

attended to, which is, that fixty on the micrometer head 
fhould hand nearly vertical, fo as to he conveniently feen. A 
few feconds of inclination to one fide or the other are of no 
moment, becaufe the dart or index being brought to that por- 
tion, whatever it may be, muft at all times remain there with- 
out alteration, unlefs fome derangement that may have hap- 
pened to the inftrument, in tranfporting from one place to ano- 
ther, fhould have rendered a frefh adjuftment neceflary. But if, 
when the wires coincide with their refpedlive dots and the firft 
notch, fixty on the micrometer head fhould happen to be under- 
neath, or fo far over from the vertex on either fide as to be feen 
with difficulty, then the gold tongue muft be moved a little by 
means of the capftan- headed fcrews, which a£t againft each other 
on theoppofite extremities of its axis. Thus, by repeated trials, 
the wiffied-for object will at length be effedted, that is to fay, 
fixty, to which the dart is to be fet, will ftand in a place eafily 
feen. But it is not to be expe&ed, that each microfcope will 
give juft nine hundred feconds for the run of fifteen minutes. 
Without great lofs of time this cannot be done ; befides that 
two obfervers, of different fights, will adjuft the microfcopes 
differently. Accordingly, in 1787, after many trials of the 
runs in meafuring fifteen minutes on the different parts of the 
limb, microfcope A was found to give only while B 

gave at a medium 90 1". But in 1788, microfcope Agave 
goo // , while B gave no more than 894/h Thefe differences 
were of courfe registered and allowed for in the eftimation of 
the angles for computation, whereby any difference between 
them almoft wholly difappeared. 

The gold tongue, which is extremely thin, applies very 
clofely to the furface of the circle. In the plan it is fuppofed 
to be feen through a thin plate of brafs covering the whole 

U z pedeftal, 


Gen . Roy’s Account of 

pedeftal, and alfo through a fmall fquare plate lying over the 
former, and fattened to it by three fcrews. In the under fide 
of this laft, there is a cavity for the projecting part of the 
tongue. This contrivance of the tongue with its dot was to 
guard againft any error that might arife from accidental mo- 
tion given to the inftrument between one obfervation and ano- 
ther, which from this precaution could never happen, without 
being immediately difcovered : for the wires being adjufted to 
their dots under the microfcopes refpeCtively, if the inftrument 
be then turned round i8o c , the wires will reciprocally bifect 
the dots that were originally oppofite to them, and thereby 
Ihew, that they are accurately in the diameter of the circle ; 
and fo on with regard to any other dots whatever. Hence 
this becomes the moft fevere mode of trying the juftnefs of the 
divifions of the inftrument. 


Art. XIV. Manner of reading of angles with the microfcopes . 

By attending to the magnified fcale at the bottom of the plate, 
it will appear, that the dot on the gold tongue, which is here in- 
verted, is about one minute to the left of zero, and alfo of the 
firft notch, with which the moveable wire alone co-incides. 
Now it will eafily be conceived, from what has been faid in this 
defcription, how readily, as well as accurately, any obferva- 
tion of an angle can be read off with fuch an inftrument ; for 
the degrees and quarters, that is to fay, the 30', or 45% 
being feen with the naked eye, and registered, the value of the 
fractional fpace between zero and the laft part grand divifion, 
feen in the field of the mierofcope, is obtained by turning the 
micrometer head until the moveable wire bifeCts the dot at 
that grand divifion. The number of notches towards the 
right hand paffed over on the fcale, equal to fo many revolu- 
tions 


the Trigonometrical Operation . 149 

tions of the head, are the number of minutes, always lefs than 
15', to be added. If there be no odd feconds, the dart will then 
ftand at 6o° on the head ; but, if any number of feconds are to- 
be added, the dart will (hew, by its pofition with regard to 6o°, 
what that number is. Thus, by adding the parts together, the 
meafure of the total angle is obtained. 

The conftrudtion, adjuftment, and application of thefe ver- 
tical microfcopes have been given more fully, becaufe they form 
a mofteffential part of the inftrument : for the fixed wire con- 
flan tly remaining on its dot, the fradlional fpace may be repeat- 
edly meafured many times over, if neceflary, anda mean refult 
may then be taken. But it rarely happens that two observers, 
reading off with the oppolite microfcopes, differ more than half a 
fecond from each other at the very firft reading. If time 
therefore permits, and the circumftances of the weather fhould 
alfo be favourable for repeating the obfervation with the tele-* 
fcope, it is fufficiently obvious to what a wonderful degree of 
accuracy the meafure of angles may in this way be obtained. 

Art. XV. Horizontal Microfcopes . 

Befides the two vertical microfcopes, applied in the manner 
that has been defcribed to the meafurement of the fradlional 
fpace in horizontal angles, there is yet another to be men- 
tioned, which is placed horizontally on the har that carries the 
tranfit telefcope, and is directed to the divifions on the femi- 
circle attached to its axis, for the meafurement of angles of 
elevation or depreffion, as has already been taken notice of 
This microfcope, which is of the fame conftrudlion with the 
others, but larger, being upwards of nine inches in length, is 
reprefented in its full dimenfion in Plate VI. It has, like the 
others, a Aide made of fteel, of fuch thicknefs as to permit, the 
7 % micrometer 


I 


130 Gen . Roy’s Account of 

micrometer fcrew to be formed of it ; and it carries a vertical 
wire placed in the focus of the eye-glaflfes, in which pofition 
it is moved parallel to itfelf from left to right, by turning the 
micrometer head. This ilide is alfo attached to a watch fpring 
which a£ts in a contrary dire&ion to the head, as in other mi- 
crofcopes of this fort. 

Each degree of the femicircle being divided into two parts 
or 30', and one revolution of the micrometer head moving 
the wire in the field of the microfcope f ; therefore in 10 re- 
volutions it changes its place half a degree or 30^ which are 
fhewn by a fcale of 10 notches in the upper part of the field 
of the microfcope, and alfo reprefented towards the top of the 
plate. Each notch correfponds to 3 minutes or 180 ieconds, 
and the head being divided into 3 minutes, and each minute 
into 12 equal parts, therefore each part is of the value of five 
feconds. 


Art. XVL Concerning the Semicircle . 

With regard to the femicircle, which has been repeatedly 
mentioned in the courfe of this defcription, it is yet neceffary 
to make fome remarks ; and particularly to (hew how, by its 
means, the axis of vifion of the telefcope, when adjufted, is 
brought and kept truly horizontal, which is effected in the 
following manner. 

Gn the oppofite fides of the horizontal bar that carries the tele- 
fcope there are fixed four fmall, but finely polifhed bell-metal 
planes, two on each fide, on the right and left of the top of the 
vertical axis, in fuch a manner as that the furfaces of the two 
on either fide are directed to or in the fame plane with the 
center of the axis of the telefcope. Thefe planes will be befit 

conceived 


the Trigonometrical Operation. ■ i $ t 

conceived by obferving attentively the top of the vertical axis 
in the fefiion towards the right hand of Plate IV. On the edge 
of the femircircle may likevvifebe feen a moveable clamD, eafilv 
made to flip, with the hand only, around its circumference, 
and it carries with it a very fine flee! fcrew. When the fp mi- 
circle is towards the left hand of the telefcope, which is its 
ordinary polition, the point of the fteel fcrew refcs, or may be 
made to reft, perpendicularly on the furface of the plane 
that is on the left of the vertical axis. But when the tele- 
fcope is inverted in its Y’s, or turned upfide down, as is the 
cafe in adjufting the line of collimation, the femicircle being 
then on the right of the telefcope, and the clamp neceflarily 
brought down, the point of the fteel fcrew accordingly refts 
perpendicularly on the furface of the plane to the right of the 
vertical axis. Thus it will be readily conceived, that in ad- 
jufting the telefcope by the level for elevations, which is then 
conftantly fufpended on its proper rod, parallel to the axis of 
vifion, the action of the fteel fcrew on the bell-metal plane 
ferves not only for the adjuftment of the telefcope in a truly 
horizontal pofition, for angles of elevation or depreffion, by 
the motion of a wire in the focus of its eye-glafs, in the man- 
ner hereafter to be defcribed, but alfo to keep it in that pofi- 
tion, by the fuperior weight of the eye end, rendered fo on 
purpofe. By the fame means the telefcope remains fteadily on 
any objedfc that it may be directed to for interfefiion, whether 
above or below the plane of the horizon * 

One thing more with regard to the femicircle muft be men- 
tioned, namely, that it gives angles of elevation \z // too great, 
and thofe of depreflion i 2 y/ too little. It is very eafy to con- 
ceive, that this arofe from the impoffibility of dividing it on 
the axis of the telefcope to which it is fixed, and through the 

centers 


1^2 Gen . Roy’s Account of 

centers of whofe pivots an imaginary line paffes that fhould at 
the fame time have pafled through the center of the femicircle. 
Mr. Ramsden took the beft method that could be devifed to 
render the excen tricity as little as pofiible. Having framed the 
femicircle, and fcrewed it in its place on the axis, he made a 
Reel point firmly fixed to the horizontal bar defcribe the con- 
centric arcs whereon the divifions were afterwards to come, and 
then marked the point for zero, when the telefcope by adjuft- 
ment had been brought as nearly horizontal as pofiible. Thefe 
previous fteps being taken, the femicircle w r as removed, divided 
on the engine, and replaced in its orginal fituation. Never- 
thelefs, when the inftrument was carried into the field, and 
fcrupuloufly adjufted, the error was found, as has above been 
faid, 12", which of courfe became the constant quantity to be 
applied with its proper fign, when angles of elevation or de- 
prefiion were taken. 

Art. XVII. Eye-glafjes of the tekfcopes , and inechanifm of the 

wires in their foci . 

It has been already mentioned, that the telefcopes of the in- 
ftrument are furniftied w T ith eye-glafles of different magnifying 
powers for ere£t and inverted vifion, fix for each telefcope, as 


follows, viz . 






Ere<ft vifion. 

Inverted vifion. 


r 

1 

/ — 



N° 

Power. 

N 3 

Power?, 


rN° 1. 

5 s. 

N° 1. 

4 . 3 - 

For the lower telefcope, < 

2. 

88. 

2% 

59 - 


3 * 

1 1 7 ' 

3 - 

87. 


N° 1. 

54 * 

N° 1 » 

4 - 0 . 

For the upper telefcope, < 

2. 

8 1, 


55 - 


n 

108. 

3 * 

80. 

Wirh 


the Trigonometrical Operation. 153 

With regard to thefe eye-glaftes, it is only neceflary here to 
mention, that thofe of the leaft magnifying powers were found 
both in day and night obfervations to anfwer the beft. 

In the focus of the eve*glafs of the lower telefcope there 
are only two wires croffing each other in acute angles, which 
are vertical, inftead of being placed at right angles, horizon- 
tally and vertically, as was the ancient method. Since the 
lower telefcope never moves through more than a few degrees 
of a vertical arc, the wires require little or no adjuftment. 
Neverthelefs this was provided for, by allowing room for a 
fmall circular motion of the end-piece, which, when adjufted, 
is then fattened by its proper fcrews, and never afterwards 
needs any alteration. 

By referring to the middle part of Plate VI. two reprefen- 
tations of the eye end of the upper telefcope will be feen, with 
the eye-piece removed. Five wires are (hewn in this end, 
namely, two that interfed each other in acute angles, fimilarly 
to thofe in the lower telefcope; and three that lie horizon- 
tally or parallel to each other. Four of thefe, viz. the two 
that form the acute angles, and the two extreme horizontal 
wires, are fixed in the focus of the eye-glaftes to the farther fur- 
face of a thin brafs Aide, fuppofed to be feen through the out- 
ward brafs, and therefore (haded more dark than the reft. This 
Aide, as will be conceived, lies neareft the eye, and is move- 
able from right to left, and, vice verfa , horizontally, for the 
adjuftment of the line of collimation, by the infertion of a 
fmall mill-head key, on a fquare pin fitted to receive it, and 
fecured by a focket on the right hand fide. The fifth or mid- 
dlemoft horizontal wire is attached to the neareft fur face of a 
fteel Aide, that lies contiguouAy to, but beyond the former. 
It is made of one entire thick piece, like thofe of the micro- 
Vol. LXXX. X fcopes, 


154 Gen* Roy’s Account oj 

fcopes, to permit the micrometer fcrevv to be formed of it ; 
and it is reprefented in the uppermoft figure attached to a 
watch fpring coiled up in the ufual manner. 

By the motion of the micrometer head, the Aide, and with 
it the wire, moves upwards or downwards in the field of the 
telefcope, a fpace equal to half the diftance of the extreme 
wires from each other. This motion above or below the cen- 
tral point, which was made to correfpond with the acute inter- 
fedtion of the wires placed in the axis of vifion of the tele- 
icope, is performed in ten revolutions of the head, as denoted 
oy the motion of the dart, ten divifions upwards or down- 
wards, in the narrow groove feen at the top of the figure. 

Now, by the means of this piece of mechamfm in the eye- 
end of the telefcope, it will appear fufficiently obvious, that 
final! angles of elevation or depreflion may be determined with 
great accuracy, when the value of a certain number of revo- 
lutions and parts (the circumference of the head being divided 
into 1 00) have been once afcertained by repeated obfervations 
of the altitude of any well-defined objedt taken by the femi- 
circle. Thus it was found, by experiment, that 7 revolutions 
of the micrometer head were equal to an angle of elevation or 
depreflion of io 7 59", or 659", on the femicircle. Whence 
it follows, that one revolution raifes ordeprefies the wire above 
or below the central point i 7 24 // .8 i^ 4> or a little more than 
B4 8r. And hence a motion of one divifion on the head railes 
or deprefles the wire nearly 4LJL ths of a fecond. 

In this manner were determined the reciprocal elevations or 
depreflion s of the feveral ftations of the feries of triangles with 
regard to each other. 

By obferving attentively the four fcrews reprefented in the 
outward end of the telefcope, a dotted groove will be feen 

under 


the T y'lgonometncal Operation . i j ^ 

under the head of each. And in the uppermoft figure there 
appears a flat brafs ring, foldered to the infide of the tube 
about half an inch from the outward end, which carries on its 
furface four ftuds to receive the lower extremities of the four 
fcrews. Thus the grooves allow room for a fmall circular mo- 
tion to be given to the end-piece for the vertical adjuftment of 
the fork of the wires, thofe that are horizontal being by con-' 
ftrudtion at right angles with it. This being done, the fcrews 
are made very fall in the ftuds below, and thereby the whole 
machinery of the end-piece is rendered perfedtly firm and 
fee u re. 

There remains yet one piece more to be barely mentioned. It 
is the prifm eye-tube, reprefented by dotted lines towards the 
right-hand fide of Plate VI. as attached to the eye dnd of the 
tranfit telefccpe, inftead of the common eye-piece with two 
convex glafles. In leaning over our inftrument to obferve the 
pole ftar, highly elevated in thefe latitudes, the body is necef- 
farily thrown into an inconvenient fatiguing pofture, whereby 
fome rilk is run of deranging the inftrument, and confequently 
of making the obfervations lefs accurately than when the ob- 
ferver can look diredtly forward, without bending the body fo 
much. For this purpole, Mr. Ramsden promifed to fupply 
the prifm tube in 1787 ; but it was only, and with great dif- 
ficulty, obtained in 1788, by which time Mr. Dalby had 
accuftomed himfelf to obferve very well without it, fo that it 
was never ufed. 

By employing this piece, light is no doubt loft ; becaufe the 
image paftes through more glafles before it reaches the eye, than 
when the common eye-piece is ufed. But for obfervations of ftars 
nearer the zenith than the pole ftar is in our latitudes, it would 
be indifpenfably neceflary. It would likewife be advantageoufly 

X a ufed 


156 Gen. Roy’s Account of 

ufed in looking at the meridian fun in fummer, for which pur- 
pofe it is furnilhed with dark giaffes, placed in a Aide moved 
by rack-work, as may be feen from infpeftion of the plate. 
They confift of three prifms, laid clofe to each other, fo as to 
form, when thus affembled, a parallelopipid. Here the green 
prifm ftands neareft to the eye, a dark one farthest from it, and 
between the two, one of white flint glafs, for correftion of 
the refraction which would otherwife take place. It will eafily 
be conceived, from the difpofition of the prifms, that the 
darkeft medium is here towards the left; and that it becomes 
gradually lighter towards the right hand, where a void part in the 
frame is brought into the field when the ftars are obferved ; or 
when, from the circumftances of the weather, it maybe unne- 
ceflary to fcreen the eye from the fun’s rays. 

Art. XVIII. General management of the inftrument for 

obfervation. 

W hen the inftrument is ufed on the ground, it is covered 
from the weather, under a circular tent, eight feet in diame- 
ter. Four Ihort piles, hooped and fhod with iron, are driven 
into the earth, and their heads levelled, by laying acrofs from 
one to the other a mahogany ftraight ruler, having a fpirit 
level attached to one fide of it. The feet of the Hand being 
then placed on piles, are firmly fattened to them by means of 
long fquare-headed fcrews, only one of which may be feen in 
the view of the inftrument, belonging to that foot which ftands 
neareft the eye. By working with the four fcrews fixed in the 
oft agonal mahogany plane, the plummet fufpended from the 
center of the inftrument is brought accurately over the point 
on the ground that marks the ftation. The fcrews of the feet, 
with the fide nuts appertaining to them, are then flackened, 

to 


the Trigonometrical Operation • t 

to give fufficient room for the adjuftment of the inftrument, 
which by them is brought to be level. 

Art. XIX. Adjufment of the axis Level. 

The axis of the upper or tranfit telefcope being brought over 
any one of the feet, and the circle being clamped, hang the 
axis level on the pivots or anfce of the telefcope, and bring the 
bubble to the two indexes ; then reverfe the level, that is, turn 
it end for end, and note the difference. Bifecft this difference, 
one half by the level’s proper adjufting fcrew, and the other 
half by that foot-fcrew only which is in a line with the axis. 
This operation being repeated until the difference wholly va- 
nifhes, the level will be truly adjufted, that is to fay, the bub- 
ble will reft between the fame points in both portions. 

Art. XX. Adjujlment of the elevation LeveL 

This level being fufpended on the rod attached to the out- 
fide of the tranfit telefcope, fcrew the ere£t eye-tube on, to 
make that end preponderate. Adjuft the bubble to the indexes 
by the fteel finger-fcrew at the tail of the femicircle’s clamp. 
Reverfe the level, and note the difference. Then bife<ft that 
difference, and corre£t one half by the finger fcrew, and the 
other half by the proper adjufting fcrew under the level, and 
fo on repeatedly until the difference wholly vaniffies. The 
level may then be hung on the two pins that project from the 
horizontal bar which carries the telefcope, where, being pa- 
rallel to the axis level, it will fhew when that is removed (as 
is commonly the cafe when terreftrial objects only are obferved) 
whether the plane of the inftrument fuffers any alteration. 
If this fliould have happened, the level on the horizontal bar 
is at all times fufficient to correft it. 

7 

5 


Art. 


Gen,. Roy’s Account of 



Art. XXL To fet the vertical Axis perpendicular. 

This may be done by either level, but beft with the axis 
level, which being fufpended on its pivots, muft be brought 
parallel with two of the feet of the inftrument ; and by the 
ferews of thefe two feet, the bubble is to be brought between 
its indexes. The circle being then turned round 180% if the 
bubble changes its place, half the difference is to be corrected 
by one of the feet ferews, and the other half by two capftan- 
headed ferews, that ad againft each other, under and belong- 
ing to one of the Y’s* or fupports, in which the pivots reft. 
When the bubble is found to be juft in thefe two pohtions, turn 
the circle 90°, which will neceflarily bring the axis over the 
third foot of the inftrument. Then corred any error there 
may be by that foot ferew. In this manner the circle will be 
made to revolve again and again, without any alteration what- 
ever of the bubble, which fhews that the vertical axis is then 
truly perpendicular to the horizon. 

Art. XXII. To make the line of Golhmation in the telefcope at 
right angles with the tranfverfe Axis . 

The pivots refting in their Y’s, dired the telefcope to fome 
diftant well-defined objed, and let the circle be clamped. 
Then reverfe the axis, that is, turn the telefcope upfide down. 
If the interfedion of the wires does not co-incide with the 
objed in both portions, half the difference muft be correded 
by the motion of the circle with the HookVjoint, and the 
other half by the motion of the brafs Hide in the eye end of 
the telefcope, by applying the milled-head key in the fmall focket 
feen on the right hand fide in Plate VI. and fo repeatedly until 
the difference wholly difappears. 

7 


Art. 


*59 


the Trigonometrical Operation. 

i 

Art. XXIII. To fet the Rod on which the elevation level hams 

par allel to the line of Collimation. 

The vertical axis being fuppofed to be nearly vertical, hang 
the level on its rod, and redify the bubble by the finger fcrew 
of the clamp. Set the horizontal wire on the fteel Hide to 
interfed the center of the oblique wires, and place the dart or 
index at zero on the micrometer head. Then obferve fome 
diftant diftind objed covered by the horizontal wire. Invert 
the femicircle, that is, turn the azimuth circle i 8 o°, and the 
telefcope upfide down, fo as to bring the wire upon or nearly 
upon the fame objed. Now, if the level be not right, redify 
it by the finger fcrew at the tail of the clamp. If the telefcope 
does not now accurately cover the fame objed as in the former 
pofition, bifed the difference by the finger fcrew of the clamp, 
and then redify the bubble by the capftan-nuts under one end 
of the rod. Repeat this operation until the level is right, 
when the telefcope fees the fame objeds in both pofitions, and 
thereby the rod will be brought parallel in altitude to the line 
of collimation or axis of vifion. 

The adjuftments of the rnicrofcopes having been already fuf- • 
ficiently explained, in giving the defcription of the eflential 
parts of the inftrument, it is unneceffary here to repeat them. 

Art. XXIV. Of the weight of the infirament, and mode of 

tranfporting it from place to place. 

The inftrument, whofe defcription and ufes we have here 
attempted to give in a general way, without reference to its 
minute parts, by a multitude of different charaders, weighed in 
tl.e whole about 200 lbs. It is contained in two deal boxes ; 


one 


jgo Gen . Roy’s Account of 

one of a circular form for the body of the inftrument ; and 
the other of an oblong fquare figure, for the tranfit telefcope. 
Within this laft box there is one of mahogany, that holds all 
the fmaller parts of the apparatus. The ftand, Reps, flools, 
pullies, ropes, tent, and canopy for the fcaffold, &c. &c. 
weighed at leaft as much more. The whole attirail was tran- 
fported from place to place, in a four-wheeled fpring carriage, 
drawn by two, and lometimes by four horfes. The carriage 
part, originally that of a crane-necked phaeton, was prefented, 
with his ufual liberality, by Sir Joseph Banks; and upon it 
was built a kind of caravan, covered with painted oil-cloth, 
whereby every thing within was kept dry and fecure. 

\ Y • x ' ' ' i -\ ■ 

SECTION THIRD. 

Defcription of various articles of machinery made ufe of in the 
trigonometrical operation referred to in Plate VII. Alfo the 
dijtinftion of the Jlations into two fets , thofe of the fecond fet 
being referred to in Plate VI [I 

i 

Article I. Portable Scaffold. 

IN the account of the meafurement of the bafe on Houn- 
flow Heath we have fliewn, that the furfaceof that remarkable 
plain is not elevated more than fifty or fixty feet above the mean 
level of the fea. From this fmall elevation, and the circum- 
ftance of its being furrounded, almoft on every fide, with lofty 
trees, it was from the beginning fufficiently obvious, that, in 
order to be enabled to make the oblervations of the collateral 

Rations 


the 'Trigonometrical Operation . 1 6 1 

ftations from the extremities of the bafe, it would be abfo- 
lutely neceflary to raife the inftrument, by fome means or 
other, to a confiderable height above the ground. For this 
purpofe the portable fcaffold, whofe plan and elevation are 
reprefen ted on the left hand fide of Plate VII. was conftru&ed. 
It confided, as may be feen, of an inward fcaffold for fup- 
porting the inftrument, and an outward one for the obfervers, 
wholly free and independent of each other, the platforms of 
both being framed about thirty* two feet above the lower ends 
of the fcantlings, which reft on the ground. Thefe being 
made of fquared deal, and the feveral parts being bolted and 
fcrewed together with many iron fcrews fecured by nuts, the 
whole could be readily taken to pieces, carried in a waggon (for 
which it made a complete load), and replaced again in any new 
fituation. This fcaffold anfwered very well the purpofe for 
which it was intended ; for the ftep-ladders, or flairs leading 
to the platform, being attached to the outward frame, the in- 
ward one that carried the inftrument remained undifturbed by 
the motion of thofe who went up and down, or walked around 
the top. The filk thread, that fufpended the plummet, was 
fecured from the effe&s of the wind by a fort of funnel or 
trunk, compofed of three deals (one fide being left open), and 
fo contrived as to be eafily turned round to any quarter of the 
heavens, whereby the open fide was always prefen ted to lee- 
ward. The inftrument was covered from the weather by a 
canvas canopy, about feven feet fquare, to which fide walls 
could be hooked for fcreening it from the wind, as occafion 
might require. By referring to the elevation it will be feen, 
that the fcaffolds, both outward and inward, might be divided 
horizontally into two parts, fo as to permit the uppermoft half 
alone to be ufed when it became un neceflary to raife the inftru- 
Vol. LXXX. Y xnent 


j6 2 Gen. Hoy’s Account of 

ment to a greater height than fifteen or fixteen feet above the 
ground. The whole together was never made ufe of, except 
at the two extremities of the Hounfiow Heath bafe. The 
uppermoft half was applied at three of the ftations only, 
namely, St. Ann’s Hill, Botley Bill, and Padlefworth near 
Dover. 

Art. II. tripod Ladder . 

Next to the feaffoid the plate reprefents, in plan and feftion, 
a tripod ladder, about thirty-five feet in height. It carries on 
its top a globe lamp, of about one foot in diameter, in which 
was ufed a fimple Argand’s burner, of a large fize, made for 
that purpofe. The lamp being removed, a focket for a white 
light might occafionally be fubftituted in its place; or (as was 
the cafe when we obferved the ftation at King’s Arbour from 
St. Ann’s Bill) a flag-ftaff might be added at the top, which 
was fecured in a truly vertical pofition, by braces fixed to the legs 
of the ladder underneath. It will be readily conceived, that by 
a contrivance of this fort a white light could be raifed to a con- 
fiderable height above the ground, if the circumftances at any 
time had rendered fuch elevation neceffary ; and that it could, by 
the help of a heavy plummet, be always placed in a truly 
vertical pofition over the point on the ground marking the fta- 
tion. The globe lamp was found to anfwer very well for fhort 
diftances of fix or eight miles, when the weather was favoura- 
ble; but it could not be depended upon in obfervations of 
diftances that were confiderably greater. 

Art. III. Common Flag faff. 

After the tripod ladder, comes in the plate the plan and 
elevation of a common flag-ftaff with its braces, carrying 
? likewife 


the Trigonometrical Operation . 1 6 3 

likewife two reverberatory lamps. Thefe two were attached 
to the fame iron bar, at the diftance of three feet from each 
other. They had concave copper reflectors, nine inches in dia- 
meter, extremely well polifhed and lilvered. They were in- 
tended at firft for experiments near London, and were very 
well feen at the diftance of fifteen or fixteen miles. To fee u.re 
us from any uncertainty that might have arifen, by miftaking 
other lights for our own, one lamp was placed over the other. 
But when we came afterwards to be better acquainted with the 
appearance of thefe lamps, that precaution was found to be 
entirely unneceffary ; wherefore fingle reverberatories were pro- 
vided, with Jpecula of ten inches diameter, and they were fup- 
plied with ftill larger burners, which could be feen at the dif- 
tance of twenty or twenty- four miles. But here it is proper to 
remark, that thefe lamps muft be carefully watched, efpecially 
in expofed windy fituations ; for if the cotton be drawn out a 
little too far, they are apt to fmoke, whereby the front glafs 
becomes obfeure, and therefore muft be wiped frequently. 
They are eafily turned on the pofts that fupport them ; and 
were, by the help of a telefcope laid on one fide, parallel to 
the axis of the rays (for which a contrivance was provided in the 
tin work) accurately prefen ted towards the ftation occupied by 
the inftrument at the time from whence they were to be ob- 
ferved. There was conftantly one of thefe lamps, and fome- 
times two, at two different ftations, burning each night, when 
we were making obfervations of the pole ftar, or white lights 
of fhort duration, placed at other diftant ftations. 


164 


Gen, Roy’s Account of 


Art. 1 V. Tripod for White Lights, 

Next after the flag-ftaff (whereon a focket for white lights 
could like wife be placed, when the flag itfelf was removed) is 
Teprefented a fnaall tripod intended for white lights only. The 
fame focket that fitted the top of the flag-ftaff, or lamp- port, 
could be applied to the tripod, by the help of three final! 
lockets fold ere d for that particular purpofe to the fides of the 
, principal one. Deal rods, of five or fix feet in height, or ha- 
zels cut from the near# hedge, ferved as the legs of this {land. 
The fockets themfelves were made of copper, becaufe thofe of 
iron would have been difiblved by the fulphur ; and the upper 
part, which was only an inch, or an inch and an half, in 
height, was fquare or round, according to the figure of the 
boxes containing the compofition, fometimes of one kind, and 
fometirnes of the other. Thefe white-light tripods, being 
readily placed by the help of a plummet over the point mark- 
ing the Ration, were found to be very convenient on the top 
of an open hill, or on the leads of a church fteeple, as the 
perfon attending them could eafily light the box with the port* 
fire, without the aid of a ladder. 

Art. V. Portable Crane . 

On the right hand fide of the plate is reprefented, in plan, 
and fe&ion, and by a larger fcale thaU the others, a portable 
crane for weighing up the inllrumenc to the tops of fuch 
towers, church ileeples, or other buildings, as became Rations 
in the feries of triangles. It was conflrudled in the Tower of 
London, and anfwered very well the purpofe for which it was 
intended, although it might ftill be improved. Before we 

were 


the Trigonometrical Operation. i 65 

were (applied with this crane, we made (Lift, by the help of 
a long beam, and a moveable treble by way of fulcrum for it 
to reft upon, to get the inftrument up to the top of its own 
proper fcaffold, and one that was ftill higher, e.re&ed over the 
tranfit room of the Royal Obfervatory at Greenwich. 

Art. VI. Reajons for changing certain Stations , 

In the courfe of the trigonometrical operation, the center 
of the inftrument has conftantly been brought, even aim oft 
to mathematical exa&nefs, over the precife point marking 
the ftation, whereby feduSions to the center on account of 
excentricity have been avoided ; and the ftation s have been 
diftinguifhed, as far as poflible, by permanent marks in fuch a 
manner, that, w 7 hile thefe remain, the center of this or any 
other inftrument may be again brought into the fame vertical 
line. By thefe means our recent obfervatlons may be repeated 
on any future occafion, and conne&ed with others, which it is 
to be hoped will be made hereafter : for this operation, the firft of 
its kind in Britain, (hould only be coniidered as the foundation 
or commencement of a feries of others, which by degrees will 
be carried to the remoteft parts of the ifland. 

By comparifon of the annexed plan of the triangles with 
that communicated to the Royal Society in 1787, as only a 
(ketch of the fcheme then propofed to be carried into execu- 
tion, it will be perceived, that fome few ftations are omitted 
entirely, and others fubftituted in lieu of fome that were then 
intended to be occupied. Of this laft number Hanger-hill 
Tower has been made ufe of inftead of Kew Pagoda. This 
laft had been propofed on a fuppofition, that without a fcaffold 
of an enormous height, it would have been impoffible to fee 
Hanger-hill Tower from King's Arbour* Neverthelefs, after 

1 a good 


! 66 Gen. Roy’s Account of 

a good deal of trouble, by cutting off the tops of certain trees, 
lopping the branches of others, and railing a flag-flaff on the 
center of the fcaffold, thefe two Rations were rendered reci- 
procally vifible. By thefe means we not only avoided making 
ufe of Kew Pagoda, which, from the nature of the building, 
would have been a very incommodious Ration ; but we thereby 
o-ot rid of Clermont Tower altogether ; and thus, inRead of 

O 

two fmall triangles, one was conflituted, larger and better, 
being nearly equilateral. 

In the introduction there has been occafiou to take notice of 
the advantage that was gained by being able to fee Frant and 
Fairlight Down reciprocally. From this circumRance the feries 
from Frant eaRward to the bafe of verification becomes in 
reality a double one, and confequently affords better means of 
afcertaining the corrednefs of the work. 

The Angularity of the fituation of Dover Caflle has like- 
wife been mentioned. Inflead of two Rations near Tatterlees 
Barn and Barefriflan, whereby it was hoped, that Dover Caflle 
might have been conne&ed with the feries to the weffward, 
it was found neceflary to make ufe of three Rations ; one at 
Padlefworth, one at Folkffone Turnpike, and a third at 
Swingfield. Thus the fide which connects that ancient fort 
with the other triangles is fliorter than was intended. But 
with fuch an inffrument as ours, and where all the angles of 
the triangles were obferved, no uncertainty arifes on that 
account. 

Art. VII. Dijlinction of the Stations . 

Having afligned the reafons that rendered it eligible or ne- 
ceflary to change fome few of the ftations propofed in the ori- 
ginal fcheme, it only now remains to enumerate the whole as 

diftinguilhed 


the ‘Trigonometrical Operation . 

diding in died Into two fets. Firft, thofe which are perma- 
nently marked by pipes funk in the earth ; and, fecondly, 
thofe where the inftrument was elevated to the top of fome 
tower, church ft^eple, or other building. The plans of the 
platforms of this laid fet are given in Plate VIII. along 
with fuch dimenfions as are neceffary to fhew, with regard 
to the fide walls, the precife fpot over which the center 
of the inftrument was placed. As often as was poftible, thefe 
fituations were further defined, by means of concentric circles 
defcribed on the leads. 

The ftations of the firft fet, marked with pipes, are fourteen 
in number, viz . 



Hampton Poor-houfe, 
King’s Arbour, 

St. Ann’s Hill, 
Hundred Acres, 
Norwood? 


• 9 


Ruckinge, 

High Nook, 

Allington Knoll, 
Padlefworth, . 


{ 


* A ® 


Botley Hill, 

Wroth am Hill 
Hollingborn Hill, 

Fairlight Down, . 


the extremities of Hounflow Heath, 
bafe. 

about the middle on the eaft edge- 
near the weft end of the garden, 
towards the Croydon end of the heights, 
jin a field belonging to Limpsfield 
l .Lodge Farm. 

in a field belonging to Mr. Johnston. 
in a field belonging to Mr. Duppbr. 

4 7 feet fou th ward from the Windmill, 
which makes with Fairlight Church, 
an angle of 105° 20 7/ . 

f the extremities of the bafe of verifi- 
1 cation. 

f an artificial mount belonging to Sir 
l John Honeywood. 

i eaftward from the Church, in the 
Broom-field belonging to Mr. Brock- 
man. 


Folkftone 


s 58 Gen. Roy’s Account of 

Folkftone Turnpike . • weftward from the Pubiic-houfe. 

The Rations of the fecond fet, where the inftrument was 
elevated on buildings, are nine in number, viz. 

Hanger-hill Tower. 

Tran (it- room of Greenwich Royal Obfervatory. 

North-weft turret of Severndroog Caftie, on Shooter’s Hill. 
Swingfield Church Steeple. 

North turret of the Keep of Dover Caftie. 

Lydd Steeple. 

Tenterden Steeple. 

Goudhurft Steeple. 

Frant Steeple. 


SECTION FOURTH. 

i 

Calculation of the feries of triangles extending from Windfor to 
Dunkirk , whereby the geodetical difance between the meridians 
of the Royal Obfervatories of Greenwich and Paris is deter- 
mined. Reference to be had to Plate IX.. 

* 

' ‘ / 

Article I. Excefs of the angles of fpherical above thofe of 

plane Triangles. 

IF the earth, or any confiderable portion of Its furface, 
was a perfect plane, an inftrument, fuch as has been formerly 
defcribed, when applied on that furface, to determine by tri- 
gonometrical meafurement the extent of the plane part, would 
every where have its axis parallel to itfelf; and the lum of the 

three 


the 'Trigonometrical Operation . 169 

three angles of each of the triangles, into whatever number, 
great or fmall, it might be divided, would conftantly amount 
to 180 0 . But the earth being a fphere or fpheroid, it follows, 
that the fame inftrument, fucceffively adjufted at each of the 
Rations, will have its axis perpendicular, on a fphere, to an 
equally curved furface ; on a fpheroid, to one unequally curved, 
in either cafe forming the horizon of the ftation ; and the fum 
of the three angles of fuch a fpherical or fpheroidical triangle 
nuift, as is known, always exceed 180 0 , lefs or more, iti pro- 
portion to the lengths of the fides. When the triangles are 
very fmall, the excefs being of courfe fmall cannot poffibly 
be difcernible by common inftruments. Even the fineft, fup- 
pofing them free from error of divifion, will fcarcely render it 
perceptible, without the utmoft care in making the obferva- 
tions. This will be fufficiently exemplified in the following 
calculations, where a column is inferted containing the fpherical 
excefs ; and another for the difference or error between that and 
the excefs of the fum of the obferved angles above 180 0 . From 
thefe it will appear, that, notwithftanding the goodnefs of our 
inftrument, and the pains taken in ufing it, we have frequently 
failed in bringing out an excefs ; and indeed the refults have 
even fometimes been in a fmall degree defe£tive. 

It had been at firft propofed to multiply the obfervations as 
much as poffible, and particularly by fucceffively changing the 
zero of the inftrument to new points (PhiL Tranf. 17 87? 
p. 219.), to meafure the fame angles on different parts of the 
circle, fo as to fubdivide any errors that might arife from in- 
accuracy of divifion, or fihake at the center. This principle, 
perfeftly good in theory, and which was adhered to as far as 
the circumftances would permit, was neverthelefs found, on 
many occafions, to be impoffible in pradtice, without facri- 
Vol. LXXX. Z ' firing 


i ~o Gen. Rot’s Account of 

t 

firing much more time than we could afford, confidently with 
the engagements entered into with the French Gentlemen, 
for the co-operation on the Coaft. At particular times, efpe- 
cially in hot weather, there was fuch a tremulous motion or 
boiling in the air, that it was only during a very fhort fpace, 
chiefly in the mornings and evenings, that the objects were 
fufficiently diftinfl to be obferved with accuracy. So difficult 
it is to do any thing perfectly good in this way, that a whole 
day has frequently been Ipent, after watching with anxious 
care, in obtaining a Angle one that was perfectly fafcisfadory ! 
At fuch times as thefe it would have been abfurd to have 
attempted to* change the zero, which always rendered it necef- 
fary to re-adjuft the inftrument by its levels. 

In very favourable circumftances of the weather a good- ob- 
iervation by day is preferable to one by the white lights at 
night ;- beeaufe, in the firft cafe, the obferver has time at his 
leifure nicely to bifeffb a fine flag-ftaff, and repeatedly to read 
off the angle ; whereas, in the fhort duration of the burning 
of the light, he is fomewhat hurried, from the fear of lofing 
fome of the lights at other diftant ftations, if two of them 
happened to come together, which now and then they did, 
from the irregularity of the rates of the watches of the artil- 
lery-men attending at the different ftations. It was, however, 
by the affiftance of the white lights only* that the moft diftant 
ftations could be rendered vifible ; and there cannot be a doubt 
that, in great trigonometrical operations, of this fort, they will 
be universally adopted hereafter. 

Sometimes an obfervation has been entirely loft, or at leaft 
that which had been obtained was not thought a very good 
one. In fuch cafes a blank has been left in the column: of 
obferved angles, and alfo in that exprefling the error. But no 

c bad 


the Trigonometrical Operation . iyi 

bad confequence has arifen on that account, there being always 
fuch other checks from the collateral flat ions, as to leave 
nothing doubtful. 

On the whole, although, for the reafons already affigned, we 
have repeated the obfervations feldorner than was at fir ft pro* 
pofed ; yet it will obvioufly appear from the refults, and parti- 
cularly from the near agreement between the meafured and 
computed length of the bafe of verification, that a few very 
good obfervations are greatly preferable to a mean that might 
perhaps have been obtained of many made in a hurry, which 
at beft would have been but indifferent. 

The quantity by which the fum of the three obferved angles 
of fpherical triangles fhould have exceeded i8o° was found as 
follows. 

Becaufe the excefs of the three angles of a fpherical 

triangle above 180° x earth’s radius = its area, therefore 

= excefs above x 8 o° in feconds, if the area and radius 

Earth’s rad. 

are taken in feconds. Now, 60859.1 fathoms being=i° on a 

'■!* 

mean fphere, we get the log. of the feet in a lecondzr 

2.0061743, and twice this, or 4.0123486 is the log. of the 

fquare feet in a fquare fecond. Therefore log. area in feet 
_ 4.01 23486 = log. area in feconds ; and the log. of the earth’s 
radius in feconds being 5.3144251, we have area in feet 
-4.0123486-5.3144251 = log. area in feet- 9.3267737 = 
log. excefs in feconds ; that is to fay, from the logarithm of the 
area of the triangle taken as a plane one , in feet , fubtradl the con - 
flant logarithm 9.32677379 an< ^ the remainder is the logarithm 
of the excefs above 180 0 m feconds nearly . 


Gen . Roy’s Account of 
Art. II. Calculation of the Triangles . 


172 


N° of 
triangles. 

Names of the Rations. 

Obferved 

angles. 

Spheri- 

cal 

excefs. 

DifF. or 
error. 

Angles cor- 

re£ted for 
calculation. 

Pittances. 

( 

Hanger-hill Tower 
(Hampton Poor-houfe 
'King’s Arbour 

0 / // 

42 2 32 

67 55 39 

70 I 48 

'// 

// 

Of// 

42 2 34 

6 7 55 39 

7 ° 1 47 

Feet. 

I. ) 


x 79 59 59 

O.29 

— 1.29 



1 

The Base between Hampton Poor-houfe anc 
Arbour 

Hanger-hill Tower from { 

1 King’s 

ar-houfe 

ir 

» 9 • « 

• • • • 

• • • • 

27404.7 
38461. 12 
37922.57 

| 

St. Ann’s Hill 
Hampton Poor-houfe 
King’s Arbour 

44 >8 51-5 
61 26 33.1 

74 *4 35 



44 18 51.5 
61 26 33.5 

74 14 35 



' . 

1 79 59 59 - 6 

0.21 

— 0.61 



1 

„ * , TT . 1t r f Hampton Poor-houfe 

St. Ann s Hill from { King t s Arbour . 

• • • • 

« • • • 

37754-25 

34455-8 


Hence, in the quadrilateral formed by Hampton Poor-houfe , 
Kings Arbour , Hanger-hill Tower , and *SV. Ann's A?///, making 
nfe of the two obtufe angles, as contained within their refpec- 
tive known fides, we have for the mean diftance of the points 
of the acute angles at Hanger hill Tower and St. Ann’s Hill, 
expreffed by a dotted line in the plan of the triangles, 68897.165 
feet. 



Wardrobe Tower ol 





Windfor Caftle 

1 • • • 

9 ® 

• Q 

58 9 58-5 

King’s Arbour 

62 40 27.5 



62 40 275 

St. Ann’s Hill 

59 9 H 


' 

59 9 *4 



0.25 




Windfor Caftle from { Si 


34819.4 

3603^-37 

N° 


the ‘Trigonometrical Operation. 1 73 


N° of 
triangles. 

Names of the ilations. 

Obferved 

angles. 

Spheri- 

cal 

excefs. 

DifF. or 
error. 

Angles cor- 
rected lor 
calculation. 

Diltances. 

f 

IV. : 

to 

Hundred Acres 
Hanger-hill Tower 
St. Ann’s Hill 

0 / // 

S 3 58 35-75 
68 24 44 

57 3,6 39 5 

// 

// ^ 

0 t // 

53 58 39.5 

68 24 44 

57 36 39-5 

• • • 

• • • • 

Feet. 

71934.2 
7921 1.22 

179 59 59- 2 5 

1.08 

- 1-83 

r Hanger-hill Tower 
Hundred Acres from | St Ann>s Hm _ 

”! 

Severndroog Caltle, 
Shooter’s Hill 
Hanger-hill Tower 
Hundred Acres 

53 3 i 

55 53 44-3 
7 ° 35 6.75 

• 


53 3 1 9-75 
55 53 44 
70 35 b.25 

• • • • 

• • • • 

84376.68 

74077.66 

l80 O 1.05 

1. 18 

- 0-13 

„ . ^ r f Hanger-hill Tower 

Severndroog Caftle from { Hundred Acres . 

"! 

'Norwood 

^Hanger-hill Tower 
Severndroog Callle 

107 53 37 
26 12 22.5 

45 54 J -5 



107 53 35-75 
26 12 23 

45 54 1-25 

9 9 9 m 

• • • • 

63673.31 

39 J 5 S-J 5 

l80 O I 

0.44 

+0.56 

- r Hanger-hill Tower 

Norwood from j Se¥e * ndr00g Caffle 

VII. i 

Norwood 

Hanger hill Tower 
Hundred Acres 

88 s 58 
29 41 20.75 
• ® ^ 



88 5 58.07 

29 41 21 
62 12 40.93 

t 

9 • • • 

35648.21 


°-53 


Norwood from Hundred 

Acres 

vm. I 

Tranfit Room, Green- 
wich Obfervatory 
Severndroog Caflle 
Norwood . 

Greenwich Obfervatoi 

III 56 50 

47 48 H 
20 14 58 



III 56 50 

47 48 13 
20 14 57 

• • • • 
• • • • 

I461O.58 
31274.4S | 

180 0 2 

0.0 1 

-j- 1 .9 

r f Severndroog 

y {l '° m {Norwood 

Callle 

• 


N° 


i?4 


/ 


Gen. Roy’s Account of 


N° of 
triangles. 

Names of the flations. 

Obferved 

Angles. 

Spheri- 

cal 

excefs. 

DifF. or 
error. 

Angles cor- 
rected for 
calculation. 

Diftances. 

IX. I 

Botley Hill 
Hundred Acres 
Severndroog C a file 

o / // 

74 37 I 7-5 
66 o 56.2 

39 21 46.25 

•// 

// 

0 / // 

74 37 18 

66 0 56 
39 21 46 

N 

• • • • 

Feet. 

48726.75 

•0104.76 

! 79 59 59-95 

0.78 

-0 88 

Botley Hill from j !* lmd 
J [ beverr 

red Acre 
idroog C 

S . 

able 

X. | 

Wroth am Hill 
Botley Hill 
Severndroog Cable 

54 25 1 

67 11 

57 4 i 49 



54 25 1 -5 

67 SI 10.21 
57 4 i 4 s -5 

• • • » 

* • • * 

72953-12 

79962.13 

180 0 1 

1. 12 

— O.12 

Wrotham Hill from { ®° tley , H ' U ‘ 

1 Severndroog Cattle 

XI. | 

1 

Frant 

Botley Hill 
Wrotham Hill 8 

50 19 19 

57 15 1 *- 2 5 
72 25 31.2 


<1 

CO 19 l8 

57 *5 11 
72 25 31 

• • • • 
• • • • 

90364.16 

79723-57 

180 0 1.45 

1 -3 

+0.15 


Frant from j 

Botley Flill 1 

Wrotham Hill ] 

XII. | 

Hollingborn Hill 
Wrotham Hill 
Frant 

« • « • 
84 12 24.5 
4« 28 37.5 

/ 


47 iy 59 
84 1.2 23.5 

48 28 37.5 

• • • • 
• • • • 

81 196.58 
107897-5 


i* 5 2 


i 

Hollingborn Hill from | 

Wrotham Hill 
Frant 

XIII. ' 

Fairlight Down * 

F rant 

Hollingborn Hill . 

48 25 53.5 

79 2 3 3 

• • • • 



48 25 55 
79 23 2 

52 11 3 

• • • 

1 13928 2 
T4 1 74 * 7 - 1 


2.85 


Fairlight Down from ( 

& 1 Hollmeborn Hill 


the Trigonometrical Operation. 


l lS 


N° of 
triangle. 

Names of the ftations. 

Obferved 

angles. 

Spheri- 

cal 

excefs. 

Diff. or 
error. 

Angles cor- 
rected for 
calculation. 

Diftances. 


O 

Goudhurft 
Botley Hill 
Wrotham Hill 

o / // 

35 26 32.5 
40 4 42 
104 28 44 

n 

// 

0 / // 

35 26 34-5 
40 4 42 
104 28 43.5 

Feet. 

XIV. 


U 9 59 5 8 -5 

I -35 

-2.85 



[ 

Goudhurft from | 

Botley Hill 
Wrotham Hill 

• • » • 
• • • • 

121809.3 

80997.43 

xv. -1 

1 

jGoudhurft 

Frant 

Wrotham Hill 

72 23 32.5 

75 33 16 
32 3 12.8 


_ . 

72 23 33.87 
75 33 J 3-63 
3 * 3 ! 2-5 



ISO O I.3 

0.81 

+ O.49 





Goudhurft from Frant 

• t # ♦ 

44389.68 

r 

XVI. < 

Hollingborn Hill 
Wrotham Hill 
Goud Kuril 

63 46 44 

52 9 11. 5 

64 4 3-5 



63 46 47 

52 9 11 

64 4 2 



09 59 59 

1.22 

— 2.22 

* 


! s. 

Hollingborn Hill from Goudhurft 

• • • • 

71296.03 

( 

fTenterden . I 

Goudhurft 

Hollingborn Hill . j 

6 7 7 55 

68 13 21 

© ■» • • 

. 



67 7 56.46 

68 13 19,5 
44 38 44-04 


XVII. J 

1 


/ j 

0.85 

! 

- 


l 

^ A , r r Goudhurft 

lenterden from J TT ... , TT .„ 

[ Hollingborn Hill 

• • • « 

• • 0 • 

54374-66 

71855.0 

! 

Fairlight Down 

Goudhurft 

Tenterden 

• 0 • • 

49 39 34 
04 59 26 



35 20 5 8 -42 
49 39 35-77 
94 59 25 - 8 i 

i 

I 

1 

XVIII. ' 



O.9I 




1 

N. 

Fairlight Down from | J 

joudhurft 

renterden 

• • ♦ • 

• • 0 • 

93625.92 

.71634-73 . 


j ~6 ' Gen. Roy’s Account of 


N° of 

triangles. 

1 

Names of the Rations. 

Obferved 

angles. 

Spheri- 

cal 

excefs. 

Diff. or 
error. 

Angles cor- 
rected for 
calculation. 

D dances 

f 

Allington Knoll 
Hollingbora Hill 
Tenterden 

/ 

ota 

4.8 24 3 8 
• • • • 
9 1 34 23 

it 

a 

0 t tt 

48 24 39 
40 O 58.96 
91 34 22.04 

Feet. 

XIX, J 

1 



1.05 




1 

Tr n r r Hollingborn Hill 

Allmgton Knoll from j Tenterden 

« ® • • 

• • • • 

96026.45 

^ 1 7 7 5.34 

i 

jLydd 

jAlliogton Knoll . 
Tenterden 

• 9 • * 

73 0 2 7 *S 
43 45 22 



6? 14 <3.82 

73 0 27 

43 45 23.18 


XX. J 

# 

1 

0.67 




l 


T . , r f Allington Knoll 

Lydd from i ^ ® . 

[ Tenterden 

a « v 9 # 

• • • • 

47849.27 

66160.93 

XXL i 

Fail light Down * 
Lydd « 

Tenterden 

54 59 l8 -s 
® ® • ® 

62 32 S3 



54 59 'IS 1 
62 27 50.18 

62 32 52.51 




O.99 




1 


Fairlight Down from Lydd 

® 9 © • 

71689.73 

XXII. ! 

Allmgton Knoll 
Lydd 

Fairlight Down 

1 

32 59 22.5 
125 42 0.25 

• » • • 

l 


32 59 23 
125 42 0 

21 18 37 

- 




°-33 




- / 

Allingt 

on Knoll from Fairlight Down 

• * 0 • 

106922.5 

1 

~ Lydd 
Ruckinge 

High Nook near Dym- 
church 

43 20 48.25 
48 58 49-75 

87 40 21.75 



43 20 48.5 
48 58 49*5 

87 40 22 

- 

XXIII., 


r 79 59 59-75 

0.21 

— 0.26 




The Base of Verification between High Nook 

and Ruckinge .... 

T , r f Ruckinge 

Lydd from | High Nook 

* 

• • • • 
• • • * 

• • • • 

28 C22»Q2 

41533-89 

1 31362.58 


N° 


the 'Trigonometrical Operation * 


N° of 

triangles. 

Names oi the Nations. 

Obferved 

angles. 

Spheri- 

cal 

excels. 

DifF, or 
error. 

Angles cor- 
rected for 
calculation. 

Diftances. 

r 

f 

* 

AUington Knoll , 

Ruckinge 

Kigh Nook 

0 / // 

9 r 2 7 20 
54 >9 1 7 
34 13 21 

n 

// 

0 / n 

91 27 i 9 . 5 

54 19 18.5 
34 13 22 

Feet. 

XXIV. J 

1 


*79 59 5 8 

0.09 

— 2.09 



1 

Aliington Knoll, from 

f High Nook 
1 Ruckinge 

• • 0 « 

_.•••• 

23184.93 

16052.44 


Hence, in the quadrilateral formed by High Nook , Ruckinge , 
Lydd , and AUington Knoll , making ufe of the two obtufe an- 
gles, as contained within their now refpedive known fides 
we have for the mean diftance of the points of the acute an- 
gles, at Lydd and AUington Knoll, reprefented by a dotted 
line in the plan of the triangles, 47849,27 feet. This dis- 
tance agrees accurately with the length of the fame fide in the 
XXth triangle, as given by the bafe meafured on Hounflow 
Heath. Here however it is to be remarked, that, in order to 
produce this agreement, the angle at Hoilingborn Hill, be- 
tween Aliington Knoll and Fairlight Down, has been made 
48° 56' 28" inftead of 48° 56' 31"!, being a difference of 
3 // t+.9 which, according to obfervation, it fhould have been. 
Had not this redudion been made, the diftance between Al- 
iington Knoll and Fairlight Down, being one of the fides of 
the XXIId triangle, would have been 106924 feet, that is to 
£ ay, if foot longer. Now, fince this fide, compared with 
the bafe of verification, bears nearly the proportion of four to 
one, it follows, that the real difference between the meafured 
length of that bafe, and its computed length deduced from 
that on Hounflow Heath, feventy miles to the weft ward, or of 
Vol, LXXX. A a either 



j _g Gen. Roy’s Account of 

either bafe with refped to its oppofite one, amounts only to 


about 4! inches. 


N° of 

triangles. 

Names of the 
Nations. 

Obferved | 
angles. 

Spheri- 

cal 

excefs. 

Diff. or 
error. 

Angles cor- j 
rented for 
calculation. 

Diftances. 


Folkftone Turnpike 
Allington Knoll 
High. Nook 

0 in 

24 17 6.25 

76 i 54 

79 4 1 °- 7 S 

// 

// 

0 / // 

24 17 6.25 

7 6 1 53-25 

79 4 i o -5 

Feet. 

XXV. ' 


180 0 1 

O.29 

+0.71 



i 

Folk (lone Tin 

f Allington Knoll 
•npike from j j| gh Noo]c _ 

• * * • 

• ® • • 

55461-7 

54706.0 

XXVI. < 

Folkftone Turnpike 
Allington Knoll 
Lydd . • 

• • • • 
109 50 40 
38 2 24 



32 6 56.89 

i °9 5 ° 39-35 
38 2 23.76 




°-59 




( 

Folkftone Turnpike from Lydd 

• • 9 9 

84659*88 

s 

Padlefworth ( • 

High Nook 
Folkftone Turnpike 

108 9 34.5 

• • • • 
57 2 0 



108 9 34.5 

14 48 25.5 
57 2 0 


XXVII. < 

) 



0.16 




1 

„ f High Nook 

Padlefworth from j Folkftone Turnp ike 

• • • • 

% • • • 

48303.7 

14713.82 

• t 

- 1 

Padlel’wort.h 

Lydd 

Folkftone Turnpike 

105 29 40.5 

9 3 8 29 

• • • • 



105 29 40 

9 3 8 29.36 
64 51 50.64 


XXVIII. > 

% 



0.27 




1 

Padlefworth from { F J ftone Turnpike 

• « ® • 
• ' • ® • 

79533-34 

14713.82 

/ 

i 

1 Padlefworth 
i Lydd 

\ Fanlight Down 

1216 3 

iS 4 5 54-75 

• • • • 


\ 

1 12 16 2.65 

i 54 5 54-4 
13 3 8 2.95 

: - 

XXIX. 



°-59 


% 


1 1 

l Pa 

dlefworth from Fairljght Down 

• • • • 

l86l I3O 
KTo 


*79 


the \ Trigonometrical Operation . 


N° of 
triangles. 

Names of the 
Nations. 

1 

Obferved 
angles. ■ 

ISpheri- 

cal 

[excefs. 

Diff. or 
error. 

Angles cor- 
rected for 
calculation. 

Diitances. 

j 

XXX. < 

I 

Swingfield . 

Padlefworth 
Folkftone Turnpike 

0 tn 

48 38 
70 S 4 5-5 

60 27 39.5 

// 

si 

0 its 

48 38 1 £ 

70 54 5-5 
60 27 39.5 

• • • • 

# # 

Feet. 

17056.06 

18525.15 

180 0 0 

O.06 

— O.06 

0 . r 1 j r f Padlefworth 

1 Swingfield from j Fo , kftone Turn[ 

• 

)ike 

r 

XXXI. - 

Dover Caftle, North 
Turret 
Swingfield 
Folkftone 

34 39 26.5 
75 3 6 40 
69 43 53-5 

■ 


34 39 26.5 
75 3 6 4 ° 

6 9 43 53-5 

• • «• • 

• • • • t 

1 

3 ° 559 - 3 2 

3 I 554 ' 5 8 

CO 

O 

O 

O 

O.13 

-O.13 

Dover Caftle from j 

[ holkitone Turnpike 


Hence, in the quadrilateral formed by Folkjione Turnpike , 
Swing fields Padlefworth , and the North T urret of the Keep of 
Dover Caftle , making ufe of the two obtufe angles, as con- 
tained within their refpe&ive known fides, we have for the 
mean diftance of the points of the acute angles at Padlefworth 
and Dover Caftle 42561. 18 feet; and hence, in the triangle, 
Dover , Folkfone Turnpike , Padlefworth , we have the acute 
angle at Dover 15 0 i8 7 44 // i, and that at Padlefworth 34 0 29' 
42 // f, as were repeatedly obferved. 


1 

XXXII. < 

/ 

Dover Caftle . 
Padlefworth 
Fairlight Down 

• • • • 

>52 15 25-5 

• e • • 



21 37 55-42 
*52 «5 2515 
6 6 39.43 




0.69 




( 

Dov 

er Caftle from Fairlight Down 

• • • • 

l86l I3.O 


jgo Gen. Roy’s Account of 


N° of 
triangles. 

Names of the 
llations. 

Obferved 

angles. 

Spheri- 

cal 

excefs. 

1 

DifF. or 
error. 

Angles cor- 
rected for 
calculation. 

Diftances. 

Feet. 

168821.07 

245777-5 

XXXIII. I 

l 

Dover Caflle . 
Fairlight Down 
Montlambert • 

1 

O / // 

• § • • 

9 © • • 

• • • • 

// 

// 

0 / // 

87 30 29.58 
43 >9 S 8 -52 
49 9 3 r -9 

• • • • 

• • • • 


7*4 


, r f Dover Cafile . 

. Montlambert from j Fairiight Down 

1 

XXXIV. ' 

Fairlight Down 
Dover Caftle . 
Blancnez 

■ 

Bis 

• • ® • 
999* 
® ® * 



25 33 55-°2 
1 10 55 29.83 

43 3 ° 35 -iS 

® • • « 

• • • • 

252469.9 

116655.93 


* 4 ^ 

CO 

1 


r f Fairlight Down 

.ncnez from [ Dpyef Caftle _ 

xxxv. i 

Dover C a file 
Montlambert 
Blancnez 

23 25 0.25 

• • t • 

• • • • 



23 2 5 °- 2 5 
36 53 18.11 
II9 41 41,64 

• * * • 

77235.0 


1.84 



Blancnez from Montlambert 


In this laft triangle, the angle at Blancnez, as determined 
with great care from a mean of many obfervations, by the 
French Academicians, was found to be 1 19° 41' 28T9, that 
is to fay, 12". 7 lefs than what refults from our obfervations 
acrofs the Channel. This difference, which is the maximum 
of the error between us in the joint operation, being fmall, 
and of no real importance one way or other, with regard t& 
the main point in difcuffion, fince it only varies the dvftance 
between Blancnez and Montlambert two or three feet, and 
the longeft fides of the triangles, which conned the two> 
Coafts, by eight or nine; it has therefore been judged bed not 

to 


the Trigonometrical Operation. 3 g 5 

to makft any alteration whatever on account of that difference 
(except as will be mentioned underneath), but to proceed 
with our own fcale of drftances for fixing the relative fituation 
of Dunkirk ; making ufe, neverthelefs, in the firft feven fol- 
lowing triangles, from the XXXVIth to the XLIJd inclufive 
of the angles as ultimately fettled by the late French opera- 
tions, which Comte ns Cassini has been fo obliging as to fun- 
ply us with for that purpofe. The angles of the XLIIId and 
XLIVth triangles are taken from M. Cassini de Thhry’s 
Book (La Meridienne verifee ) ; and thofe of the XLVth tri- 
angle refult from the combined operation. 

In conformity with the exception above alluded to, we have, 
in the XXXVIth triangle, added 3" to our angle obferved at Do- 
ver between Elancnez and the fleche of the fpire of Notre Dame 
at Calais ; that is to fay, inftead of 12° 46'' 39" it has been made 
12° 46' 42", on a fuppofition, that the fpire may overhang fo 
much from the perpendicular towards Blancnez : becaufe the 
fpace between the pofition of the white light on the gallery, 
and' the axis of the fpire, being carefully meafured by Dr. 
Blagden, correfponds to an angle of 9", whereas the obfer- 
vation gave only a difference of 6 ". 


N° of 
triangles. 

Names of the ilations. 

Angles cor- 
rected for 
calculation. 

D iH:ac ces. 

( 

1 

1 

XXXVI. 

N.D, at Calais , , . 

Slancnez iignal „ . 

Dover Caftle . e 1 2° 46' 39" 

>t t> a. /■> 1 • c 1 Dover Caftle , 

N.D. at Calais from i _ . 

1 Elancnez iignal 

Excefs above i8o°“0 // .S4. 

0 / // 

47 27 & 

IT 9 46 12 

12 46 42 

Feet. 

r 57449-9 ! 
35 0 23-3 1 


N° 


182 


Gen. Roy’s Account of 


N° of 
triangles. 

Names of the ftations. 

Angles cor- 
rected for 
calculation. 

Diftances. 

f 

XXXVII. <1 

Fiennes fignal. . . . 

Blancnez; fignal 

Montlambert fignal 

r \ C f Blancnez fignal . 

Fiennes fignal from | Montlambm fignal 

0 / // 

94 26 27.5 

51 18 27.3 
34 15 S- 2 

• t • • 

• • • • 

Feet. 

43600.8 

60464.4 

r 

XXXVIII. < 

V. 

N.D. at Calais . . • 

Fiennes . . 

Blancnez 

N.D. at Calais from Fiennes 

64 21 43. 1 
46 24 25.2 
69 13 51.7 
• * • • 

415219.6 

XXXIX. « 

Watten . • 

N.D. at Calais 

Fiennes . • 

r f Fiennes 

Watten from | N>D . a( Ca , ais 

27 37 14.8 
66 30 36.2 
85 5 2 9 

• 9 J • 

• • • • 

89453-5 

97283.0 

r 

XL. < 

Dunkirk • • 

Watten 

N.D. at Calais 

^ . c f N.D. at Calais 

Dunkirk from ^ 

[ Watten 

5 1 39 
$5 57 46.5 
42 23 1.5 

• • • • 

* • • • 

‘ 23734-8 

83616.2 

r 

XLI. , 

Mont-Caffel • • • 

Dunkirk . * • 

Watten ^ 

_ K ^ rr 1 f f Watten 

Mont-Caffel from | Dun]drk 

63 24 50 
42 7 12 

74 27 58 
• • • • 
• • • • 

62711.1 

90087.5 

! XL II. ' 

;Hondfe6te 

Dunkirk 

Mont-Caffel . • 

r A f f Mont-Caffel 

Hondfcote from | Dunkirk _ 

93 3 1 34 -i 
5 i 7 4-5 
35 21 21.4 

• t t » 

• • • • 

70260.7 

52228.4 

XLIII. | 

Dunes, fignal at the eaft end of the bafe • 

Dunkirk . . % • 

Hondfcote . . 

Signal on the Dunes from f p^^k^ . 

81 57 3 ° 
4 « 43 23 

49 ! 9 7 

• • • • 
• • • • 

39641.0 

40000.5 

! 

XLIV. { 

1 

'[Dunes fignal . 

Fort Revet s, weft end of the bafe • 

...Dunkirk 

\\ _ . . . r f Signal on the Dunes 

lj Dunkirk from | Fo 5 n Revers 

1 Fort Revers from the Dunes, the meafured bafe 
But this bafe by meafurement was • 

The difference is . 

5 19 47 
90 17 29 
84 22 44 

• • • • 
• • • • 
• • • • 
9 t t • 

• • • • 

40000.5 

37 1 5 - 6 

29808.7 

39801.7 

7.0 


I11 


i 


the Trigonometrical Operation. z g 

In order to complete the triangular connection between 
Greenwich and Paris, there remains yet one triangle more (the 
XLVth) to be given, whereby we fhall be enabled to connect 
the point M near Dunkirk with Dover. For this purpofe it is 
neceflary to make fome remarks on the Dunkirk bafe ; and 
alfo to ihew, from the French operations, how the point M is 
fituated with refpeCt to Paris, Dunkirk, and Calais. 

M . Cassini de T. hury, in his book already quoted (p. 22. and 
54.) has informed us of the manner in which this bafe on the 
Strand near Dunkirk was meafured ; and that its mean length 
amounted to 6224.36 toifes, which are equal to 39801.7 Eng- 
liih feet. Thus it appears, that there is a difference as above 
ftated of feven feet in defeCt, between the meafured and com- 
puted length of the laft fide of a combined feries of 44 Britifh 
and French triangles, depending on a bafe meafured on Houn- 
flow Heath, and verified by another meafured in Romney 
Marfli. But a feries of 24 French triangles, founded on a 
bafe meafured near Paris, and corrected by another executed 
near Amiens, gives for the length of the fame bafe near Dun- 
kirk 39809.94 Englifh feet, and confequently only an excefs of 
15 inches with regard to our refult. This very near agree- 
ment in the determination of the fame length by two different 
ieriefes of triangles, whofe extremities are fituated at fo great a 
difiance from each other, fufficiently proves the excellency of 
trigonometrical meafurement, and fhews to what a wonderful 
degree of accuracy operations of this fort may be brought 
when fine inftruments are made ufe of, and great care bellowed 
in the application of them. Doubtlefs fmall errors may have 
arilen in the progrefs of the work, unfeen on both fides ; but 
thefe falling fometimes one way and fometimes the other, they 
feem fo far to have compenfated for, or deftroyed each other, 

3 that 


Gen. Roy’s Account of 

that their effects have almoft wholly difappeared. With regard 
to the deficiency of feven feet found between the a&ual mea- 
furement with the deal rods, on the Strand near Dunkirk, and 
the trigonometrical refult, it is necefl'ary to call to remem- 
brance what would have happened, if the bafe on Hounllov/ 
Heath had been meafured with our deal rods when in their 
greateft hate of expanfion from the moifture they had imbi 1 = d. 
In the volume of Philofophical Tranfa&ions for 785 p. 
438. it has been fhewu, that our bafe would thereby have bee 1 
rendered more than feven feet and a half too (hort. i aw, 
although the French rods were covered with feveral coats of 
oil-paint to prevent their imbibing the fait water, which we 
are told retted on the Strand at particular places fix inches 
deep ; yet it is prefumable, that it would be impoflible to pre- 
vent it from entering by the extremities at the jundion of the 
ferrules, and extending along the fibres, underneath the paint. 
Hence, in all likelihood, the intended remedy would prove 
worfe than the difeafe : for the paint might prevent the rods 
from dryinf fo foon as they otherwife would have done, and 
thereby the meafurement would be given ftill fhoitcr than it 
no paint had been applied. Whether this fuppofition may be 
thought to be well founded or not, is left to the determination 
of thofe who are converfant in matters of this fort. But the cu- 
rious fad, one way or other, might be afcertained by means of 
fuch a fteel chain as ours, in the fpace of one or two days 
at moft. For, fuppofing the extremities of the bafe between 
Fort Revers and the Dunes to be accurately known, and the 
alUgnement traced out on the Strand only with camp colouis, 
placed at reafonable diftances from each other, and a moveable 
cord, by the fimple application of the chain on the common 

furface, without any extraordinary apparatus whatever, for- 

, wards 


the Trigonometrical Operation * % g ;♦ 

wards and again backwards, the diftance might certainly be 
determined within a foot of the truth. And hence the impor- 
tance is obvious of having at all times fo accurate and eafy a 
mode of meafurement. 

On due confideration of all thefe circumftances, it will not 
be thought furprifing, that in fixing the fituation of Dunkirk 
and the point M near it, where the meridian of the Royal 
Obfervatory at Paris interfeds a line drawn from thence to 
N.D. at Calais, the Dunkirk bafe , with the corrections de- 
pending upon it, are here receded ; and that the fcale of dis- 
tances furnifhed by the Britifh triangles is adhered to, as not 
differing fenfibly from the mean refult given by the other two 
French meafurements. 

From M. de Cassini’s Book, La Meridienne Verifies , p. 5 1 „ 
53 * and 56. it appears, that Dunkirk (rejeding the corredions 
formerly alluded to) is north from the Royal Obfervatory at 
Paris 125522.2 toifes, which are equal to 133775.3 fathoms. 
And from p. 51. and 57. it further appears that, by the mean 
of two fuites of triangles, Dunkirk is eafi: from the meridian 
of Paris 1420.41 toifes, which are equal to 1513.8 fathoms* 
Again, at p. 276. of the fame Book, Dunkirk is faid to be north 
I2 55 x 7 toifes, and eafl 1430 toifes, which are refpedively 
equal to 133769.7 and 1524.2 fathoms. And, laftly, at p. 
36, of the Defcripiion Ge'ometrique de la France , of the fame 
Author, publifhed in 1783, and which being the lateft fhouk! 
of courfe be the moft corred work, Dunkirk is made north 
from the Royal Obfervatory 125495 toifes, and eaft from its 
meridian , only 1416 toifes, which are refpedively equal to 
1 33746.3 and 1509.1 fathoms. Now, without pretending 
here to enter into the inveftigation of the various corredions 
+ and — which have been applied to the angles of the tri- 
Vol. LXXX* B b angles^ 


x 86 Gen . Roy’s Account oj 

angles, to bring out thefe different refults, we (hall abide by 
the firft, that being immediately produced by the mean of the 
obfervations without any arbitrary correction whatever ; and 
being, with regard to eafting, nearly a mean between the two 
extremes ; and fince we have it in our power to fettle with 
great precifion the longitude of Dunkirk, and likewife the 
point M, with regard to Greenwich, we (hall then be enabled 
to determine the difference of longitude between the two Royal 
Obfervatories within a mere trifle of the truth. 

By Comte de Cassini’s triangles, executed in the autumn of 
1787, and communicated in January 1789, it appears, that 
Hondfcote is fouth-eaftward from the meridian of Dunkirk 
6?° 53 ' 2Q,/ 5 which angle being fubtradled from the total 
angle between Hondfcote and Calais 144 0 53" 28 // .5, being 
the fum of the three angles at Dunkirk in the XLth, XLlft, 
and XLIId triangles, there remains 77 0 o / 8 '. 5 for the angle 
that Calais is fouth-weftward from the meridian of Dunkirk. 
And this laft angle being again fubtrafted from 180°, we have 
102 0 59 / 51" . 5 for the angle between the fame meridian pro- 
duced northward, and a line drawn from Dunkirk through M 
to Calais. 

Now the two diftances 13 3775*3 and 1513*8 fathoms being 
feverally reduced in the proportion of 39809.94 to 39808.7 
the two lengths affignable to the bafe on the Strand near Dun- 
kirk, as formerly eftablifhed, we have 1 33 771.1 fathoms for 
the diftance in Britifh meafures of the parallel of Dunkirk 
from that of the Royal Obfervatory at Paris; and 1 51575 
fathoms for the diftance of Dunkirk eaftward from its meri- 
dian. Again, making ufe of the angle 7 7 0 o' 8A5, and its 
complement to 90°= 12° 59' 51A5, we have 1553.56 fathoms 
for the direCl diftance between Dunkirk and the point M ; 

2 alfo 


the Trigonometrical Operation, t$7 

alfo 358,6 fathoms for the fpace that M is font h ward from 
Dunkirk. But the diftance of Dunkirk from the Royal Ob- 
fervatory at Paris, given in the 276th page of M. Cassini de 
Thury’s Book, when reduced in the proportion of the two 
bafes becomes 133765.7 fathoms, and taking a mean between 
this number and that formerly found 133771.1 fathoms, we 
have for the mean diftance of Dunkirk from the Obfervatory 
133768.4 fathoms, from which fubtracting 358.6 fathoms, 
the mean fouthing of M from Dunkirk, there will ultimately 
remain 1 33409.8 fathoms for the diftance between M and the 
Royal Obfervatory at Paris, meafured on the meridian. 

Now, fince in the XLth triangle we have the diftance of 
N.D. at Calais from Dunkirk 123734.8 feet, if from this num- 
ber we fubtradl 1553.56 fathoms = 9321.36 feet, there will 
remain 1144 13.4 for the diftance of the point M from Calais. 
Thus, with the fupplemental angle to 360° at Calais, viz. 
139° 17' 3 3" -2, contained within its now known fides, 
we are finally enabled to complete the XLVth triangle, and 
thereby to determine the fituation of M with regard to Dover, 


XLV. 


f N.D. at Calais 
\ Dover Caftle 
1 M near Dunkirk 


N.D. at Calais from 


f Dover Caftle 


1 M near Dunkirk 

Dover CafUe from M 
Alfo, Dover is from Dunkirk 


139 17 33-21 The fpherical ex- 
18 24 37.3 !*cefs above i8o 0 n: 
22 *7 49-5 J 2"-42. 

Feet. 

1 37449-9 
. • 11 44 I 3'4 

236273.7 
243295,3 


Art. III. Refult of the trigonometrical operation , in as far as relates 
to the geodetical filiation of the different fattens , with regard 
to the Royal Obfervatory at Greenwich . 

Having, by the preceding calculations of the lengths of 
the fides and meafures of the angles of a continued feries of 

B b 2 forty- 


1 


2 88 Gen. Roy’s Account of 

forty-five triangles, determin'd the relative fituation of every 
Ration with regard to thofe neareft adjacent to it, we are next 
to (hew, from thefe data y and the angles which Norwood and 
Severndroog Caftle make with the meridian of Greenwich 
Obfervatory, the fituation of each Ration with refpedl to that 
meridian, to its perpendicular, and alfo the direft or diagonal 
diflance with the bearing from the Obfervatory itfelf. Thefe 
various determinations are contained in the fix firR columns 
towards the left hand of the annexed table of refults, wherein 
the Rations are likewife diftinguifhed into two fets, as fituated 
to the weft ward or eaftward of Greenwich. 

By means of a fcaffold, perfeflly fimilar in principle to that 
formerly defcribed, but more flight as being made for the tem- 
porary purpofe only, the ftand of the inftrument was railed to 
the height of thirty-eight feet above the floor of the tranfit- 
room of the Obfervatory. At this elevation all the furround- 
ing objects which we wifhed to obferve (St. Paul’s excepted, 
which is hidden by the camera* turret of the great room) could 
be diftindtly feen, and the angles between them and the fouth 
meridian mark accurately meafured. As that mark is but at a 
fhort diftance, namely, about 1500 feet from the tranfit, and 
eonfequently _ J ^th* of an inch correfponding to about a fecond 
of an angle on the mark, it was therefore very neceflary that 
the center of the inftrument fhould be brought with great pre- 
clfion over the center of the axis of the tranfit-telefcope un- 
derneath. In this operation, and indeed in every other while 
at Greenwich, the Aftronomer Royal gave us his beft afliftance. 
In the firft place, the central point of the axis was determined 
by the interfe&ion of diagonal lines drawn acrofs the fquare 
pari in the middle. On this fquare part, when the telefcope 
was in its horizontal pofition, a bafon of quickfilver was 

placed, 


the ST ngonometrical Operation . 1 8 9 

placed, having a fmall crofs made of two thin bits of wood 
fitted to the infide of the bafon, and lying very near the fur- 
face of the quickfilver, in fuch a manner as to make the center 
of the crofs co-incide with the interfe&ion on the brafs under- 
neath. A fmall perfpedtive glafs being then fixed in a move- 
able board under the center of the inftrument, this was made 
to Hide at right angjes to itfelf in the diredtion of the meridian 
and that of the axis of the tranfit, until the center of the crofs co- 
incided with the axis of vifion in looking downwards. The 
board being there faftened, and the perfpedtive removed, the in- 
terfedtion of filk threads ftretched acrofsthe board, marked very 
accurately the point correfponding with the center of the tran- 
fit, over which the center of our inftrument was brought by 
the help of the plummet. The fecond method was ftill more 
diredt. Dr. Maskelyne had an objedt glafs prepared for his 
tranfit telefcope of a focus fuited to the vertical height of the 
ftand of our inftrument above it. This glafs being applied to 
the tranfit, and the aperture contradled by a piece of pafte-* 
board with a circular hole in the middle, a very fmall pin-hole 
being likewife made in the board at top, the fame was grar 
dually moved by diredtions from the obferver below, looking 
through the telefcope in its vertical pofition, until the pin-hole 
nicely co-incided with the axis of vifion. The inftrument 
was then brought as before, by the help of the plummet, 
exadtly over the pin-hole. In this manner, which was that 
adhered to, no doubt remained of more than about T A„th part 
of an inch, with refpedt to the center of the inftrument being 
in the interfedtion of two vertical planes pafling through the 
axis of vifion and that of motion of the tranfit underneath* 
After having remained a week, the, co-incidence of the pin- 

1 hole 


I0o Gen. Roy’s Account of 

hole with the axis of vifion of the telefcope was tried, and 
found to have ftiffered no alteration. 

In the VUIth triangle, the angle at Greenwich, between 
Severndroog Caftle on Shooter’s Hill and the ftation on Norwood 
heights* hath been fhewn to be m° 5 6 ; 50". By feveral obfer- 
vations on different parts of the circle, Norwood ftation was 
found to be weftward from the meridian 38° f which of 
courfe leaves for the angle that Severndroog Caftle is eafhvard 
from it 73° 49 / 34 x/ ; and either of thefe two angles is fup- 
pofed to be within a very fmall fradtion of a fecond of the 
truth. 

Now, with the fides and angles of the feries of triangles 
already known, and the angle 38° f 1 W' now given, which 
Norwood makes with the meridian of Greenwich towards the 
weft, it will befufficiently obvious to thole who are in the leaft 
acquainted with plane trigonometry, that the diftances of that or 
of any other ftation of the feries, from the meridian of Green- 
wich and from its perpendicular, are eafily obtained. Never- 
thelefs, that thofe who are but little converfant with matters 
of this fort may themfelves be able to examine the computa- 
tions whereby the columns towards the left-hand of the an- 
nexed table have been fupplied, we fhall give one example, 
which will ferve for the whole. 

Suppofe (Plate X. fig. 1.) GM to reprefent the meridian of the 
trail fit- room at Greenwich ; GW the perpendicular to that 
meridian produced indefinitely towards the weft ; N the ftation 
at Norwood, and H that at Hundred Acres, whofe diftances 
are required, that is to fay, weftward from the meridian, and 
fouthward from the perpendicular : then through the ftations 
N and H, let dotted lines be drawn parallel to the meridian 
and perpendicular refpedtively, whereby four parallelograms 

will 


the Trigonometrical Operation. t g t 

will be formed. In the firft, or that which is neareft to Green - 
wich, having GN in the VUIth triangle given -31274.48 
feet, and the angle NG« = 38° f it", with its complement 
NG^=5i° 52' 44", it follows, that Nw reprefenting the dif- 
tance of Norwood weftward from the meridian 15=19306.54 
feet; and Np reprefenting its diftance fouthward from the per- 
pendicular is = 24603.86 feet. Again, by attending to, and fum- 
ming up the angles round the point N, we Ihall find the angle 
GNH = 1 75 0 44 / 36 // .82,vvhich wanting 4 0 15' 23 // .i 8 of 180°, 
Ihews that the direction of the fide NH inclines fo much more 
to the weftward than the angle NG«. Wherefore NGw=38° 
7 16 +4 15 23 .18 = 42 22 r 39 // .i8 = HN s, is the angle 
which the line NH makes with Nr, a parallel to the meridian of 
Greenwich drawn through the point N. Now, in the fupple- 
mental parallelogram, having the diagonal NH = 35648.21 
given in the Vllth triangle, and the angle HNr = 42 s 2 z' 39". 1 8, 
alfo its complement = 47° 37' 2 o".8 2 , making ufe of NH as 
radius, and thefe two laft angles refpedively, we have rH — 
24027.36 feet for the fpace that H is more weftward than N; 
and wH = 26334.04 feet, that H is more fouthward than N. 
Hence ®N + rH = 433 33.9 feet is the fpace that H is to the 
weftward of Greenwich; and />N + wH = 50937.9 feet is the 
fpace that H is fouthward from the perpendicular to the meri- 
dian of Greenwich. Laftly, with thefe two given fides, and the 
contained angle 90°, we find the angle MGH=r 4 o° 23' 18^.54, 
that Hundred Acres is fouth-weftward from the meridian of 
Greenwich; whence the dired or diagonal diftance GH = 
66876.73 feet. Now, by referring to the table of refults, for 
the two firft ftations weftward from Greenwich, the numbers 
brought out in this example will be found in the left-hand co- 
lumns under then reipedive heads, and fo it would be with 

the 




X g Z Gen . Roy’s Account of 

the reft. In another place we (hall have occafion to point out, 
how the columns towards the right-hand of the fa id table have 
been filled up. 

i 

SECTION FIFTH. 

On the difference between horizontal angles on a fphere and 

fpheroid . Plate X. 


IN the Paper of 178 7, various computations were given 
concerning the figure and dimenfions of the earth, founded 
chiefly on the a6tual meafurement of different arcs of the 
meridian in different latitudes, fome of them very remote from 
each other. From the alternate comparifon of thefe refults it 
appeared, that the figure afligned to the earth by M. Bouguer 
in his fecond fpheroid agreed better with thefe meafured por- 
tions of the curve, as fo many data , than any of the other 
hypothefes . Hence it naturally occurred, that the trigonome- 
trical operation which we were then about to commence 
might probably throw fome further light on this intricate fub- 
je£l, which, for a great length of time, has engaged a confi- 
derable fhare of the attention of the fcientific world. In the 
confideration of this matter, a new and curious point, not for- 
merly attended to, and immediately connected with our ope- 
ration, prefented itfelf for inveftigation, viz . fuppofing the earth 
to be a fpheroid , fuch as M. Bouguer’s, confiderably flattened at 
the poles , what might be the difference between horizontal angles 
obferved with a fine inflrument on that fpheroid , and on a fphere ? 

The 


/ 


the Trigonometrical Operation. jgg 

The following folution * of that important problem, being the 
only unexceptionable one that 1 have received, is here given in 
the author’s (Mr, Dalby’s) own words. 

Let CE and CP (Plate X. fig. 2.) reprefen t the equatorial 
and polar femi-diameters of the earth, confidered as a fpheroid 
flattened at the poles; P£ and PN two meridians ; pe and pn 
two correfponding ones (that is, in the fame planes) on a 
fphere, having the fame center C. Let the points a , h , A, B, 
on the fphere and fpheroid have the fame latitudes refpedlively. 
Draw the radii tfC, b C, and the verticals AG, BW. ' 

Then, becaufe the angles AON, BDE, in the fpheroid, are 
always equal to the latitudes of the points A, B, thefe angles 
are therefore refpedtively equal to the angles aCn 9 bCe , in the 
fphere, and confequently the verticals AG, BW, are parallel to 
the radii tfC, bC. 

Let the latitude of B or b be greater than that of Aori?; 
and let it be required to make the horizontal angle PAr on the 1 
fpheroid equal to the angle pab , or what the horizontal angle 
would be on the fphere. 

Becaufe the angle pab is meafured by the inclination of the 

1 / 

planes, aCb , aCp , and AG is the common interfeftion of all 
the planes of the vertical circles at A, and is parallel to aC 9 
and in the fame plane ; therefore, when the horizontal angle 
PAr is equal to the angle pab ? the planes GAr, CA muft be 
parallel to each other ; and confequently Gr, the line where 
the plane GAr interfefts the plane of the meridian EP, is pa- 

* From my correfpondence by letter, and otherwife, with Dr. Maskelyne, I 
had reafon to hope, that he would have favoured me with lome communication 
on this fubjeft. No doubt, he has been prevented by other bullnefs , but he will 
probably give his method of folving fpheroidical triangles to the Royal Society on 
feme future occafion. 

Vol. LXXX. C c 


raiiel 




3 <24. Gen. Roy’s Account of 

rallel to C b in the fphere, or WB in the fpheroid. Hence, if 
from G, the point where the vertical AG meets the axis, we 
draw Gr parallel to the vertical BW, it will give the point r in 
the meridian EP, making the horizontal angle PAr equal to 
the angle pah, or what the horizontal angle would be on the 
fphere. 

In like manner, if the angle PB'U is to be made equal to the 
angle pbq, Wv muft be drawn parallel to GA, ancj the plane 
<nWB will be parallel to the plane AGr ; and therefore the 
angles of the fpheroidical triangles PAr, PuB, as mealured by 
the inclination of the planes, are equal to each other refpec- 
tively, and equal to the fpherical angles of the triangle pab. 

From hence it follows, that if A be the place of an inftru- 
nient which meafures horizontal angles in the meridian NP on 
a fpheroid, and BT a flag-ftaff fet perpendicular to the furface 
of the earth on another meridian EP, the obferved horizontal 
angle PAB, between the meridian PA and the flag-ftaff BT, 
will be greater than it would be on a fphere (the latitudes and 
longitudes being the fame in both) as long as the latitude of 
the flag-ftaff is greater than that of the inftrument, the excefs 
being the angle BAr ; but if the latitude of the inftrument is 
the greateft, as fuppofe it was at B, and the flag-ftaff at A, 
then the obferved angle PBA will be lefs than it would be on 
the fphere, the defed being the angle AB^, which, becaufe 
the planes W*uB, GAr, are parallel, will be the fame as the 
excefs on the other fide. 

If the latitudes of the points A and B are the fame, the 
planes WvB, GAr, will coincide, or the verticals will meet in 
the fame point in the axis, and therefore the obferved angles 
will be equal to each other, and the fame as they would be if 
obferved on a fphere. 


Becaufe 


the 'Trigonometrical Operation . ipj 

Becaufe AG, ‘lAV, BW, rG, are parallel to aC, AC, the 
angles vWB, AGr, will be equal to the angle aCb, or arc ab , 
therefore the arcs ^B, Ar, will each be equal to the arc ab ; 
that is, they are arcs of great circles of the fame value, in- 
tercepted between the meridians PN, PE, at B and A. 

Draw GR perpendicular to the vertical BW ; then, becaufe 
BW and rO are parallel, it will alfo be perpendicular to ; G ; 
and becaufe the axis PW is the common interfeftion of the 
planes of all the meridians, and BW, rW, are in the plane 
of the meridian PB, therefore GR is in that plane ; and be- 
caufe the angle WBr, made by the vertical and meridian, and 
the angle GRB, are right ones, therefore GR is equal to the 
arc Br nearly, and confequently is nearly equal to what fub- 
tends the difference of the horizontal angles on the fphere and 
fpheroid. 

And if GS be perpendicular to the vertical GA, it will be 
equal to the arc Av nearly, and therefore GR, GS, or the arcs 
Br, Av, will be as the cofines of the latitudes of B and A. 

Draw AK the tangent to the meridian at A, to meet the axis 
CP produced ; alfo draw AH perpendicular to the vertical AG, 
to meet Gr produced ; through H draw KHT, and join AT, 
Then, becaufe the points K, PI, are in the plane of the hori- 
zon of A, the line KHT will be in that plane ; and becaufe 
rH and BT are in the plane of the meridian BP, therefore HT 
is alfo in the fame plane, and is what fubtends the angle TAPI, 
the true difference of the horizontal angles, which, when the 
fpheroid is given, may be determined as follows. 

From the nature of the fpheroid, find the length of the ver- 
tical AG ; alfo the points G and W, where the verticals meet 
the axis : then, becaufe the angle AKG is equal to the latitude 
of A, and AGH is its complement, GK and AK will be given. 

C c 2 Let 


Jf j 6 Gen. Roy’s Account of 

Let a and b on the fphere have the fame latitudes and difference 
of longitude as A and B on the fpheroid, and find the angles 
pah, pba , and the arc ab , or angle aCb ; then becaufe AG is 
given, and the angle AGH equal to the angle aCb, AH will 
be given ; with AH and AK, and the included angle HAK. 
(equal to the fpherical angle bap) find the angle AHK, and 
alfo KH ; then, becaufe the triangles KHG, KTW, are in the 
fame plane (that of the meridian BP) and GH is parallel to 
WT, thefe triangles will be fimilar. Hence GK : HK :: 
WG : TH ; now HA, HT, and the included angle AHT (the 
complement of AHK) being given, the angle TAH, the differ- 
ence of the horizontal angles, will be given. 

Example. Let the fpheroid be that of M. Bouguer; and let 
the latitude of A be 49 0 40', of B 50°, and their difference of 
longitude c° 3c 7 . 

From the nature of the fpheroid, the radii of curvature of 
the meridian at the equator and the pole, will be 3465507 and 
3524069 fathoms nearly; their difference is 58562 fathoms, 
the length of the evolute of the meridian ; and the vertical 
AG = 3465507 4-Jh.x 585624-4 x 58562 x fine 49 0 4o'V + T 4 r 
x 58562 x fine 49^ 40')“ = 3509769.5 fathoms; alfo OG = T l 
x 58562 +_ 4 T x 58562 x fine 49° 40 1 2 = 40307.66 fathoms; 
and DW zz JL x 58562 + Jt- x 58562 X fine 50°* = 40397.23 
fathoms. Now, the angles GOC, WDC, being = the lati- 
tudes of A and B, we get CG = 30726 .i 6, and CW =.30946.08 
fathoms, their difference being 219.92 fathoms = GW. 

The fides pa, pb, being equal to 40° zo' and 40° refpe&ively, 

and the included angle = 3c/, will give the angle pab — 43 0 

■ - • ■ • * 

5i / .48".2,, the angle pba — 135 0 45' i 6 "a, and ab, or the 
angle aQb, = 2/ > 


Now 


the Trigonometrical Operation. 197 

Now, by proceeding as directed above, we get GK =r 
460423 2. 9, AK= 2980006.3, and AH = 2841 2.2fathoms. Hence 
the angle AHK = 1-3.5° 4 $' 20". od, and KH = 2979745.4 
fathoms; whence HT= 141.37 fathoms, This, with AH, 
and the included angle AHT = 44 ° * 4 ' 39" - 9 2 (the comple- 
ment of AHK.) give the angle TAH- 1 T 58". 9 , the difference 
between the horizontal angles on the fphere and fpheroid. 

Hence the obferved angles at A and B would be 43° 5 T 48". 2 
+ ii' 58 // .9 = 44° 3 ' 47 "- and *35 45 ' 1^.2-iT 58A9 

=1 35 ° 33 ' i 7 " 3 - — 

If the figure is an ellipfoid having the fame axes, the angle 

TAH will be found = 8 / 4T4. 

It may be remarked, that the angle TAH, or the horizon^ 
tal angle TAK, diminifhes or augments as the point obferved 
in TB is elevated or depreffed ; this variation is however too 
fmall to be worth attending to in practice, as may be (hewn in 
the following manner. 

Let the fpheroid be M. Bouguer’s (becaufe the difference 
will be greater than on an ellipfoid) ; and let the points A, B, 
fig. 3. have the fame latitudes and difference of longitude as 
above ; alfo, let BT be the flag-ftaff, and through B draw 
GBn. 

Now, if we fuppofe B to be in the horizontal line nearly* 
the horizontal angle at A, taken between the north part of the 
meridian AP and the flag-ftaff at B, will be the angle BAP, 
the telefcope in this cafe being pointed to B, and the vertical 
plane which it would then move in is the plane nBGA ; but if 
the telefcope is directed to fome pointT in the flag-ftaff above B, 
the angle TAP in this cafe will evidently be lefs than it was 
in the former by the angle n AT nearly; and.confequently.it 

diminifhes as the obferved point T is elevated ; and it is alfo 

a evident. 


i pS Gen , Roy’s Account of 

evident, that it will be augmented as the point obferved is 
below B. 

The latitudes of A and B being 49^ 4c/ and 50°, and their 
difference of longitude 3c/, BG will be nearly equal to AG, or 
3509769 fathoms, and GR being equal to 141.36 fathoms, 
and the angle GRB a right one, we have BG (3509769) : rad. 
:: GR (141.36) : fin. 8", the angle GBW, or T Bn. Now, 
fuppofing the point T to be a mile above the furface, this with 
the angle tzBT = 8 7 , will give T n equal to about three inches ; 
but T/z is in the plane of the meridian PBE, and confequentiy 
would be feen obliquely, if viewed from A, becaufe the angle 
ABT is about 135°, and therefore T n muft fubtend a very 
fmall angle at the diftance of 33 \ miles, which is nearly the 
diftance between A and B. 

From the determination of the horizontal angles that would 
be obferved at A and B (fig. 2.) on the fpheroid, if AP, BP, 
the co-latitudes of A and B are known, and the angles ABP, 
BAP, are given by obfervation, it follows, that the greater of 
thefe obferved angles muft be augmented, and the leffer dimi- 
nifhed, by the fame quantity of a degree, till the fum and dif- 
ference give the oppofite fides AP, BP, accurately by fpherical 
computation, and then the third angle, or difference of longi- 
tude, will be given : for the obferved angles at B and A being 
refpeftively 135 0 33" 17 A3 and 44° 3' 47 // .i, we have fine 
I 35 ° 33 ' I 7 - /, 3 ’+ ll/ 5 s "- 9 : fine AP :: fine 44 0 f 47"* - 
u / 58 /x .9 : fine BP accurately; but taking the angles that 
would be obferved, fine 135° 3 f 17A3 : fine AP :: fine 44 0 3 ' 
47 : fine of an arc greater than BP ; and fine 44 0 3 / 4y // .i 
: fine BP :: fine 135 0 33' if ^3 : fine of an arc lefs than AP; and 
this will fhew if the obferved angles are confiftent, as angles that 


the Trigonometrical Operation. 199 

onght to be found by obfervation on a fpheroid flattened at 
the poles. 

Becaufe the fum of the obferved angles at A and B on the 
fpheroid are equal to the fum that would be obferved on a 
fphere, the latitudes and difference of longitude being the fame 
on both, and the differences equal, therefore the fum for com- 
putation is the fame for both, and the quantity of each for 
computation on the fpheroid may be found from the following 

Theorem . 

In any fpherical triangle BPA (fig. 4.) if two of the fides 
PB, PA, and the fum of the oppofite angles, PBA + PA.B, 
are given, it will be, 

As the tangent of half the fum of the fides. 

Is to the tangent of half their difference ; 

So is the tangent of half the fum of the angles , 

To the tangent of half their difference . 

In the fpherical triangle abp (fig. 2.), as fine bap : fine bp :: 
fine abp : Sm tap-, that is, on the fpheroid, fine BdP : fine 
BP :: fine <i;BP : fine AP. Now, the arc Bv being = the arc 
ha, confidered as an arc of a great circle, it follows, that in 
the fpheroidical triangle vBF, if vB , BP, and the included 
angle vBB are given, the other angles at P and v may be found 
by fpherical computation, but not the third fide . Suppofe 
BP, B'u, are given, and the included angle uBP a right one; 
then rad. : fine BP :: cotang. Bv : cotang, angle BP<u ; there- 
fore, if the latitude of the point B, and the angle BW n J, or 
the quantity of the arc Bv, as an arc of a great circle perpen- 
dicular to the meridian at that point, are given on a fpheroid, 
the difference of longitude may be found by fpherical compu- 
tation, but not the latitude of the point v. 


But 


zco 


Gen . Roy's Account of 

But if the fpheroid is known, the latit ice of a given point 
(v) in a great circle -perpendicular to ? ?e meridian, mav be 
found nearly from what has been deliver’d above. Thus, as 
rad. : cofine BP :: cofine Hv : cofine or an arc (FA' lei s than 
Yv, the co-latitude of v. 'Now, with the latitude (tuppofe of 
the point A) thus found, and the given latitude of B, find GS 
(fig. 2.) which will be very nearly equal to the arc Av, and 
the value of this, as an arc of the meridian, being added to 
PA, will give Pv 7 the co-latitude of v. 


SECTION SIXTH. 

* , * 1 

Manner of determining the latitudes of the fations . Application 
of the pole far obfervations to computations on different fpheres y 
and alfo on M. Bouguer’s fpheroid , for the determination of 
the differences of longitude . Ultimate refult of the trigonome- 
trical operation , whereby the difference of the meridians oj the 
Royal Obfervatories of Greenwich and Paris is determined* 
Plate X 

Article I. Preamble , foewing the general principles adopted 
for fettling the latitudes of the fations . 

In the Paper of 178*7, fo often quoted, and which was in- 
tended only as a iketch of the mode then propofed to be fol- 
lowed in conducting the recent trigonometrical operation, we 
had occafion to fihew, that the meafured arc of the meridian 
between the point M near Dunkirk, and Perpignan fituated at 

the 


201 


the Trigonometrical Operation * 
the bottom of the Pyrenean mountains, correfponding to an 
arc in the heavens of nearly 8 °| of latitude, differed but little 
from what .Should be its true length, fuppofmg the earth to 
have the figure and dimenfions affigned to it by M. Bouguer 
in his fecond fpheroid. Here, however, it is become neceffafv 
to take notice of fome miftakes * that, through inadvertency, 
were fallen into in the computed lengths of the arcs, which,, 
although they affe<3 in a certain degree the accuracy of the 
numbers brought into comparifon, do not invalidate the general 
reafoning there advanced, and the only thing meant to be efta- 
blifhed, namely, that JVX. Bouguer. s hypothefis anreed better 
with actual meafurement on different parts of the fu.r face of 

* The miftakes adverted to in the text were of three kinds. Firft, an erro- 
neous mode of fumming up the lengths of the arcs from the lengths of the 
degrees, although thefe taken feparately were very accurately computed : for 
enhance, the 43d was taken as that extending from 42 to 43, whereas it fliould 
have been taken for the middle point, that is, from 42 j to 43J, and fo on in 
regard to others. Hence the arcs are all made fomewhat too long. The fecond 
was the omiffion of the value of 93I toifes in eftimating the length of the 
celeflial arc between Greenwich and Perpignan, the fe£tor with which the ft ars 
were obferved having ftood fo much to the- northward of the church of St. Jaumes, 
the point to which the triangular meafurement correfponded. The third was 
fallen into from not knowing that the French obfervations of the ftars had 
been corrected for the nutation of the earth’s axis, in a Paper of M. de la 
Caille s, inferted in the Memoirs of the Academy of Sciences' for the year 
1 758 j whereby all the lengths of the celeftial arcs were thereby in fome degree 
changed from what had been affigned to them refpedlively in the Book, La 
Merldienne verifiee, publiftxed in 1744. From the fame Paper it further appears, 
that they rejedfed altogether their obfervations at Perpignan, as being probably 
affedled by the attradtionof the Pyrenees. With regard to that part of the Table of 
Comparifon in the Paper of 1787, which is affeaed by thefe errors, the only 
dung that now can be done is to annex to this paper a correaed flip, which may 
be leferred to occafionally, or cut off and pafted over the former. 

Vol. LXXX. d a 


the 




2Q2 Gen. Roy’s Account of 

the earth, than any of the others with which it was com- 
pared. 

In proof of this, we need only for the prefent remark, 
what will be made fully to appear hereafter, that the diftance 
between the parallels of Greenwich and Dunkirk, or Green- 
wich and M, being now added (by our trigonometrical opera- 
tion) to the meafured length of the meridian of France, the 
meafured and computed fedtions of the united meridian will be 
found to agree almoft exadtly at Paris ; that the excefs of the 
meafurement is but of the value of 3" or 4" at Bourges; only 
of b" at Rodes ; aud even as low down as Perpignan, com- 
prehending in the whole an arc of the heavens of more than 
8°j, the excefs is not greater than what would anfwer to be- 
tween 16" and 17", the chief part of which is probably ow- 
inv to the attraction of the plummet of the fedtor by the Py- 
renees. In the Paper of 1787, the effeCt had been a {Turned at 
a quantity equal to about 10". But every thing on this head 
muft be confidered as merely matter or fuppofition, which 
cannot be determined one way or other until triangular mea- 
furements fhall have been extended beyond the Pyrenean moun- 
tains into Spain, and correfponding obfervations of the ftars 
made on both fides with the fame inftrument, which mould be 
one of the beft that could poffibly be invented for the purpofe. 
In the mean time, fince the French have rejefted their own 
obfervations at Perpignan, we (hall avoid drawing any conclu- 
fions with regard to latitudes from the obiervations to the 
fouthward, and confine ourfelves to thofe immediately con- 
nected with our operation, made at the northern ftations of the 
meridian. 

In carrying on the trigonometrical operation, it never was 
propofed that we (hould attempt to determine the latitudes of 

the 


the Trigonometrical Operation . 2 o 3 

the Rations, by adlual obfervations of the zenith difiances of 
fiars, which, with the very beft inftrurnents hitherto ufed for 
that purpofe, could not have been done nearer than about \ /f 
of an angle in the heavens, anfwering in thefe parts to 101 feet 
on the furface of the earth. Even if we could have been fupplied 
with a fedor fo far furpafiing the old ones' (fuch perhaps as Mr, 
Ramsden may hereafter invent) that would have given zenith 
diftances to one- tenth part of a fecond, or about ten feet on the 
furface of the earth, the .application of it in our operation 
would have been mere lofs of time : for the Aftronomer Royal 
having fettled the latitude of Greenwich 51 0 28' 40"; to 
within lefs than half a fecond of the truth ; and the geodetical 
fituation of each Ration of our feries being determined fo accu- 
rately with regard to that point, as to leave no where an uncer- 
tainty of more than one or two feet; we have thereby been 
able to determine the relative latitudes to a fmall fraction of a 
fecond. Here, however, it is to be underftood, that we have 
adhered to M. Bouguer’s fcale, as anfwering almofi exactly in 
the narrow fpace of 26' 51", or thereabout, of latitude be- 
tween Greenwich and M, to which our operations have been 
confined. 

That this mode of fettling the latitudes of our Rations is 
extremely accurate, will more fully appear from the following 
confiderations. In the general computation of fpherical tri- 
angles, a fphere whofe diameter is a mean between the longeR 
and fhorteft of M. Bouguer’s fpheroid has been adopted, be- 
caufe it was obvious, that in our latitudes the degree of fuch a 
fphere could not differ fenfibly from the mean degree of the 
fpheroid. Thus the degree of the fphere 60859.1 fathoms 
anfwers (as may be perceived by confulting the table in the 
Paper of 1 787) the degree of the meridian on the fpheroid in 

D d 2 the 


20 a Gen. Hoy’s Account of 

the latitude of 51 3 f. Again, if the total length of one- 
fourth part of the fpheroidical meridian of the earth, between 
the equator and the pole, 5478094.4 fathoms be divided by 90* 
(Fig. de la Terre de Bouguer, p. 310. and 311.), we fhall 
have 60867.72 fathoms for the mean degree of the meridian, 
which in the fame table will be feen not to differ fenfrbly from 
that anfwering to the latitude of Greenwich ; in or near which 
parallel the curves of fuch a fphere and M. Bouguer’s 
fpheroid interfeft each other, as will be readily conceived by 
referring to and confidering the rcprefentation of them, in 
Plate X. fig. 3. 

Art. II. Of the pole-far obfervatlons in general. 

It became neceffary, in the preceding article, to point out 
in what manner the latitudes of our ftations have been de- 
duced from their relative fituation with regard to Greenwich ; 
becaufe the method adhered to of fettling the differences of 
longitude by the obfervations of the pole-ftar, which could 
rarely be made except on one fide, that is to fay, at night, 
when the ftar was eaftward from the pole, implied as a matter 
of courfe, that the latitude of the ftation fhould be accurately 
known, for the computation of the ftar’s azimuth. With the 
declination of the ftar, fettled to fo great a nicety as it has 
been by the Aftronomer Royal, and the latitude of the place 
given, a fingle azimuth was fufficient for obtaining imme- 
diately the true direction of the meridian. Much time would 
have been ufeleflly loft in attempting to get obfervations of 
the ftar in day-light when on the weft fide of the pole, whereby 
the double azimuth would have been obtained ; and in that 
cafe the bifedlion of the angle would have given the true me- 
ridian of the place, without the knowledge of its latitude. 

For 




the Trigonometrical Operation . 205 

For the purpofe of the pole-ftar obfervations a fmall table 
had been previoufly computed, of the exad times of the ftar’s 
being in the eaft and weft ; whence the moments of its greateft 
elongation were readily known. On thefe occafions the Board 
of Longitude’s premium watch, by the late Mr. Harrison, 
was made ufe of. Its rate of going all the time that it was in 
the field in 1787, was very uniformly 9I feconds a day fafter 
than mean time. But in the winter months the watch gra- 
dually changed its rate from plus to minus , and when it wai 
carried into the field in 1788, and, during the five weeks that 
it continued there, it regularly loft on mean time from 3! to 
4 feconds each day ; having in that fhort interim been twice 
compared in Argyll- ftreet, with an excellent clock made by 
Gumming, with an improved Ellxcot’s pendulum. 

With regard to thefe pole-ftar obfervations, whereby the 
differences of longitude, or the angles of convergence of the 
meridians towards each other, have been determined, it is 
neceflary to remark, that although feme few were made to the 
weftward of Greenwich, yet thefe were not at fufficient dis- 
tance from it, and alfo taken of too ihort fides, to afford 
refults that were perfedly fatisfadory and conclufive. It is on 
the obfervations to the eaft ward only, and chiefly on thofe 
made at Goudhurft and Botley Hill, which are upwards of 
twenty-three miles from each other, and reciprocally vifible, 
that we have relied for the fcale of degrees of a great circle 
perpendicular to the meridian in thefe latitudes ; whence thofe 
of longitude have been obtained. The obfervations made at 
Folkftone Turnpike, which is upwards of fifty-eight miles in 
dired diftance from Greenwich, and where, fortunately, the 
double azimuth of the pole-ftar was obtained, are perfedly 
confident with thofe taken at Goudhurft and Botley Hill. But 

when 


206 Gen. Roy’s Account of 

when at Fairlight Down we had no obfervations of the ftar, 
being at that time fo much engaged with the other effential bufi- 
nefs of the triangles, and particularly with the interfeftion of the 
lights on the Coaft of France, as to render it impoffible to 
attend to any thing elfe, even if the weather had proved lets 
unfavourable than it was at the period alluded to, for celeftial 
obfervations. 

Art. III. Pole-far obfervations at Goudhurf and Bothy Hill 
applied to computations on the mean fphere . 

Let B (Plate X. fig. 5.) be Botley Hill ; PER its meridian ; 
GGoudhurft; W Wrotham Hill ; T Tenterden; RG an arc 
of a great circle paffing through G, and falling perpendicu- 
larly on the meridian BR ; alfo let % % rep refen t the circle of 
the pole-ftar’s apparent declination; and B*-, G*, be two 
azimuth circles touching that circle. 

Auguft 14, 1788, at Goudhurft, the angle 
#GT, or that between the pole-ftar, when at its 
greateft apparent diftance from the pole on the eaft 
fide of the meridian, and the reverberatory lamp 
at Tenterden was obferved t, • • 104 32 19I 

The angle BGT, between the lamp at Botley 
Hill and Tenterden, was repeatedly obferved, 167 43 56 

Their difference — angle -*GB is, , 63/1 36! 

f The obfervations of the pole-ftar at Goudhurft and Botley Hill were repeated for 
feveral nights at each place ; but thefe here given are the inoft exa£t. At Goudhurft 
the angle which the ftar made with the lamp being noted, the telefcope removed, and 
the plane of the inftrument being turned 180 0 , or half round, the telefcope re- 
placed and directed again to the ftar, the difference on the circle was found to be 
only i"J. The fame method was univerfally adhered to in all places where 
obfervations of the ftar were obtained. At Botley Hill, in particular, the dif- 
ference between the readings was no more than i"4. 

Auguft 


the 'Trigonometrical Operation. 


207- 


Auguft 23, 1788, at Botley Hill, the angle 
&BW, or that between the pole-ftar at its greateft 
apparent elongation and the lamp at Wrotham 
Hill, was obferved, . . . 76 21 27 

The angle WBG, by repeated obfervations, was, 40 4 42 

Their fum = angle *BG is, . . 1 16 26 19 

In order to obtain the ftar’s azimuth at each place, we may 
take, without producing any fenfible error, the latitudes of G 
and B, as they would be found on M. Bouguer’s figure, 
which we have already announced, and will hereafter prove to 
be confiftent with obfervation. Thus B, or Botley Hill, is 
fouth from Greenwich 72882! feet, and nearly on the fame 
meridian; wherefore its latitude will be 51 0 16 7 4i /7 .54, and 
its co-latitude BP of courfe 43' i 8 7 '.46. Now, P% 

the apparent diftance of the ftar from the pole at that time 
beings c° 49 7 22 / .§4, in the right-angled fpherical triangle 
P-^-B, we have fine BP : rad. :: P* : fine 2 0 54 / 54 // .2 equal 
to the angle -&BP, the ftar’s azimuth from the north. And 
this being added to the angle -^BG obferved 1 1 0° 2 b 7 we 

have the angle -&BP = 1 19 0 2i 7 13R2 for that comprehended 
between the meridian and Goudhurft. 

The diftance of Goudhurft from the perpendicular to the 
meridian of Greenwich is 132592 feet, and its diftance from 
the meridian of Botley Hill, on a perpendicular to that meri- 
dian, is 106171 feet nearly = GR. Hence the latitude of the 
point R is 51 0 6 7 52A89 ; therefore RP — 38 0 53' , and 

RG =106171 feet=; I7 7 1 9 7/ -7 nearly. Hence, as rad. : cofine 
KP :: cofine RG : fine 51° 6 7 49 7/ . 7, the latitude of G nearly; 
therefore GP — 38° io 77 .3 ; and P*- the ftar’s apparent 

diftance at the time being i Q 49 / 25A34, we have the angle 

PG 


20 g Gen. Roy’s Account of 

PG*, the ftar’s azimuth = 2° 54' 20". 8, which being fub- 
traded from the angle BG* obferved at Goudhurft between 
the lamp on Botley Hill and the ftar, there remains the angle 
BGP = 6o° if 15". 7 comprehended at Goudhurfr, between 
Botley Hill and the meridian. 

Now with thefe data let us fuppofe, in the fir ft place, the 
earth to be a fphere, whofe diameter is a mean between the 
longeft and Ihorteft of M. Bouguer’s fpheroids, the latitude of 
B, and of courfe its co-latitude BP, given ; alfo the angles 
PBG and PGB refpedively 119 0 2t / i3' / .2 and 6o° if if'.J, 
we fhall then have PG the co-latitude of G, and the angle 
BPG or difference of longitude of B and G. And becaufe the 
degree of fuch a fphere contains 60859.x fathoms, the latitude 
of* Botley Hill will then be 51 0 16 41 '.45, and BP its co- 
latitude = 38° 43' 1 8 / -55- This laft fide, with the former 
angles PBG and PGB refpedively 1 1 9° 21' 13". 2 and 60^ if 
if'.j, give PG= 38° 53' 6A72 the co-latitude of G ; and alfo 
the angle BPG, the difference of longitude of the points B 
and G equal to 2j' 36".']. Again, in the right-angled 
fpherical triangle PRG, rad. : tang. GP :: coline of the angle 
RPG : tang. 38° 53' 3 ,/ .47 = RP. But the point R is 22094 
fathoms fouth from Greenwich, and nearly on its meridian, 
therefore its latitude will be 51 0 6' 52G8 ; and hence PR the 
co-latitude will be 38“ 53' 7". 2, which exceeds PR formerly 
found by fpherical computation to be 38^ 53' 3A47 ^y 3 //# 73’ 
an arc equal to 63 fathoms. Alfo EG, the diftance of Goud- 
liurft from the meridian of Botley Hill, on a perpendicular to 
that meridian, is equal nearly to 1 7695 fathoms, which, allow- 
ing 60859.1 fathoms for a degree, correfponds to an arc of 
if 2b". 7. But fpherical computation formerly gave RG = 
if 20", the difference confequently is 6".y = 1 13I fathoms; 

therefore the earth cannot be this mean fphere, which was 

afl'umed 


the Trigonometrical Operation . toy 

affumed for the purpofe of exemplification, becaufe its degrees, 
in the direction of the meridian, differ fo little in thefe latitudes 
from thofe of M. Bouguer’s fpheroid. 

Art. IV. 'The fame pole far ohfervatlcns applied to computations- 

on a fphere of greater dimenfons . 

Let us fuppofe, in the iecond place, the earth to be a fphere 
of fuch magnitude as to have degrees of a great circle con- 
taining 61253! or 61254 fathoms, we ill all then get the lati- 
tude of B or Botley Hill 1=51° i6 ; 46 /r , the latitude of ft = 
51 0 f 1A2, and PR = 38°52 / 5 8 ' 8 ; alfo RG = 1 f 19A9. 
Now, BP— 38° 43' 13A9, and the obferved angles will give 
the angle BPG, or the difference of longitude — zf 3 6 A/ .7, the 
fame as before, and the arc PG or co-latitude of G = 38° 53' 
2 // .05 *. This la ft fide, with the angle RPG:=: 27' 36.7 of 
the right-angled fpherical triangle PRG, will give P R ^38 1 
5 2 / 58" 8, and RG — if 19V9; that is to lay, the obferved 
angles PBG and PGB, at Botley Hill and Goudhurft reflec- 
tively, are nearly the fame as they would be found on a fphere of 
fuch magnitude as to have degrees containing 6 1 253 J 01*61254 
fathoms. But fince the value of RG as an arc of a great cir- 
cle was before found by the triangles BPG and RPG to be 
17' 20", when the latitude of B was taken as belonging to a 
fphere whofe degrees contained 60859.1 fathoms Rand the 
fame arc as now determined, viz. if 19A9, agrees very nearly 

* It is evident, that as the latitude of B increaf^s, the ftar’s azimuth, or the 
angle SfBP, and confequently the angle PBG, increafe likewife. But at G the 
angle PGB is diminiflied by the increafe of the angle GP, or the azimuth ; and 
therefore if the difference of the latitudes of B and G remains the fame, or 
nearly the fame, the fum of the angles PBG, PGB, will alfo be nearly the fame ; 
wherefore no fenfible difference in the angle BPG, or difference of longitude, will 
be found on this account. 

Vol. LXXX. 


Ee 


with 


2io Gen. Roy’s Account of 

with the former, although the latitude of B be now taken on a 
fphere whofe degrees contain 61253! fathoms, it obvioufly 
follows, from thefe recent obfervations, that whatever the prc- 
afe figure of the earth may be, or the ratio between its diameters , 
the degree of a great circle upon it perpendicular to the meridian , 
cannot in thefe latitudes differ much in length from 6 1 fathoms. 

Art. V. The pole far obfervations at Folkfone Turnpike applied 
to computations on the fame greater fphere. 

Let G (Plate X. fig. 6.) be Greenwich; PR its meridian; 
F, H, and T, the Rations at Fairlight Down, High Nook, and 
Folkfione Turnpike, refpe&ively ; alfo let PF and PT be me- 
ridians paffing through F and T ; and FR and T r great circles 
cutting the meridian of Greenwich PR at right angles in R and r . 

At the Ration T, on the 7th of September, 

1788, at night, the angle between the pole-flar, 

when at its greateR apparent elongation from the 

pole on the eaR fide of the meridian, and the re- 0 , „ 

verberatory lamp at H, wasobferved, . 1 23 1 9 3! 

On the following morning, Sept. 8th, the 
angle between the Rar, when at its greateR 
diffance on. the weR fide, and the flag-Raff at H, 
was obferved, . . • IX 7 3 ° 5 2 ^ 

The difference or double azimuth is, . 5 48 io| 

And the half fumis, . . 120 24 57.87 

This half fum 120° 24'' 57 // .8y * is the angle PTH, or that 
comprehended between the meridian PT and H. The angle 

HTF, 

* By taking the latitude of T as determined on M. Booguer’s fpheroid,— 
-j° 2' 45^.3 nearly, the co-latitude or TP is equal to 38° £ 4 / * 7 > an( ^ 

flax’s apparent diftance at the time being 1° 48' i 8".03, we have, as fine 

38 ° 


I 


21 t 


the Trigonometrical Operation . 

HTF, or that between the lamp at H and the white lights 
repeatedly fired at F, was twice obferved 22' 48" ; therefore 
120 0 24 ' 5 7". 8 7 + 22' 48"= 120 0 47 / 45.87 is the angle PTF, 
that the Ration on Fairlight Down makes with the meridian of 
Folkftone Turnpike. 

Now, rT being equal to 45827.88 fathoms, and RF = 
2 '’884.68 fathoms, if we take 61253! fathoms = 1°, we fhall 
have Gr= 22871 fathoms = 22' 24 // . 18 ; GR = 36436.1 fa* 
thorns = 35' 41 '".42} rT = 44' 53^-4 ; and RF = 23' zf'-JS % 
therefore PR, the co-latitude of R, will be 39 0 7' and 

that of r or P r will be 38’ 53' 44". 18. Hence, in the right- 
angled fpherical triangle PRF, we fhall have the angle RPF = 
nj' 4". 901, and PF = 39° 7' y^.294- Further, the triangle 
PrT gives the angle rPT=T 11' 29". 143, and PT = 
38° 54' j^.98. Now, i° 1 1' 29 // .i43-37 / 4 ,/ .90i = 34 / 
24 /, .242=the angle FPT. This laft angle, with the twct 
containing fides PT and PF, give the angle PTF= 120° 47' 
44 // < 75, the fame as it was actually obferved very nearly. And 
hence we have another ftrong proof, that on this part of our 
earth the degree of a great circle , perpendicular to the meridian , 
cannot differ much in length from 61253! fathoms, whatever may 
he its real figure, ‘which cannot be determined until thefe obferva- 
tions fhall have been compared with others that may hereafter be 
made in the fame way , and with equal care , in latitudes remote 

1 

from each other . 


38° 54' 1 4". 7 : rad. :: fine i° 49' l8".03 : fine 2° 54' 5". I a the tar’s azimuth. 

Twice this angle, or 5 0 48' io' / . 24 > a S rees ver y near ty w * t ^ 1 the double azimuth 

5 0 48' Io"|, found by the obfervations on the yth and 8th of September. This 

near agreement, at the fame time that it ferves to fhew the accuracy of thefe. obfer* 

vations in particular, and the goodnefs of the mode that was adopted in general, 

ferves alfo to prove, that Dr. Maskelyne has fettled the declination of the pole® 

tar to great precifion. A 

t? p. 'j Art# 


E e 2 


212 


Gen . Roy’s Account of 


Art. VI. The latitude of the point M near Dunkirk, and con fe- 
quently the dijlance between the parallels of Greenwich and M, 
deduced from the fame length of a degree perpendicular to the 
meridian . Alfa the comparifon of its length with that rf the 
meridional degree . 

Again, let us fuppofe G (Plate X. fig. 7.) to be Greenwich ; 
P r its meridian ; M the point near Dunkirk, fuppoled to be in 
the meridian of Paris; Mr a great circle palling through that 
point, and falling perpendicularly on Pr. Then, if we take 
61253! fathoms ===1°, we (hall have rM (—89674,7 fathoms) 
^ l ° 2 f 5 ° f - 37 1 and Gr ( = 25831 .43 fathoms) = 25 ' i 3 // .iy. 
Hence Pr will be 38° 56' 38^'. 1 7 ; and therefore as rad. : cofine 
Pr :: cofine rM : fine 51 0 1' 58". 5 the latitude of M ; and <i° 
28 / 4o // -5i° i y 5 8 7/ . 5 ~26 / 4i // .5 is the difference of latitude 
between Greenwich and M, or the diftance of their parallels. 
Now, as 3600" : 61253! :: 26' 4 1 /x . 5 (= i6oi" 5) : 27249.3 
fathoms; and this being added to 133409.8 fathoms, the meafured 
arc of the meridian between M and the Royal Obfervatory at 
Paris, we have 160659.1 fathoms for the length of the ter- 
reftrial arc of the meridian comprehended between the parallels 
of the two Royal Obfervatories nearly. But the length of the 
celeftial arc between them being 2 0 38' 26" would, at the 
rate of 6 1 253! fathoms to a degree, give= 1 6 1 743.3 fathoms, 
which exceeds the meafured arc by 1084,2 fathoms. Therefore 
it is fujfciently obvious , that the earth cannot be a fphere of thefe 
dimenfons ; but it mufi be an oblate fpheroid , on which a degree of 
a great circle , perpendicular to the meridian , in this way of con- 
fidering it , exceeds in length the mean degree of the meridian be- 
tween Greenwich and Paris in the proportion of 61253! to 
60842, or 4 1 1 f fathoms. 


Art. 


the ’Trigonometrical Operation . 21 g 

Art. VII. Application of the refults of the pole-far obfervations 
to computations on M. Bouguer’s fpkeroid, for the difance of 
the parallels of Greenwich and M. 

Hitherto the refults obtained by the geodetical meafurement 
and pole-ftar obfervations have been applied to fpherical com^ 
putations on two fpheres fuited to the different lengths of de- 
grees found in two oppofite directions, at right angles to each 
other, the meridian and its perpendicular ; and from thefe 
computations it has been clearly proved, that the earth cannot 
be either of the affumed fpheres. 

Let us therefore, in the next place, fuppofe the earth to 
have the figure, and the dimenfions of M. Bouguer’s fpheroid, 
and by way of comparifon apply the fame refults to computa- 
tions on that figure. Thus the latitude of the point r will be 
found 51 0 f 12T09, and the arcrMzr T 27' 49 // .03„ Hence,, 
as rad. : cofine rP :: cofine rM : fine 51° T 48 // .85 the lati- 
tude of M nearly. Now, let the points r and M be repre° 
fen ted by B and v (Plate X. fig. 2.) then will A reprefent the 
point whofe latitude is 51 0 T 48T85 ; and by proceeding in 
the manner formerly directed for a fpheroid, we get GW~ 
15.12 fathoms = to the diflance in the axis between the points 
where the verticals from the latitudes 51° f iT'.oy and 51 0 i< 
48T85 meet the faid axis. Hence, as rad. : 15.12 (GW) :: cofine 
51° i' 48". 8 5 (angle SWG) : 9.509 fathoms =: GS, or the arc Av 
extremely near. Now the value of Av, as an arc of the meridian, 
is o / 7 .5 6, which being added to 38° 58' n^.15 (AP), gives 
38 58' 1 1T71 mP'u, the co-latitude of v ; and hence the true 
latitude of v 9 or M (fig. 7.), is 51 0 1' 48". 29, which being 
fubtradled from 51° 28' 40", the latitude of Greenwich, there 
remains 26' 5 1 1 for the arc between them, or diflance of 

their 


214 Gen. Roy’s Account of 

their parallels, which on this fpheroid correfponds to 27248.2 
fathoms, lefs only by 1.1 fathom than the fpace found, in the 
laid article, to anfwer to an arc of 26' 4i /7 .5, being the dii- 
tance of the fame parallels on the greater fphere. 

Thus the meafured length of the arc between Greenwich 
and M, 27248.2 fathoms, being added to the meafured dis- 
tance of M from the Royal Obfervatory at Paris, we have for 
the total length of the arc between Greenwich and Paris 
160658 fathoms, which exceeds the computed length or the 
fame arc on M. Bquguer’s hypothecs by no more than 7 f 
fathoms. 

Rut it hath been already fhewn, that whatever the precife 
figure of the earth may be, a degree or a great circle upon it, 
perpendicular to the meridian, cannot in thefe latitudes differ 
much in length from 6125.51 fathoms, being but i6| fathoms 
Jefs than 61270 fathoms, the length of the correfponding 
degree on M. Bouguer’s fpheroid. 

As far therefore as we are enabled to judge from the refult 
of thefe obfervations, the earth differs but little either in its 
latitudinal or longitudinal dimenfions from what hath been 
affigned to it by M. Rquguer. 

Art. VIII. .Application of the pole far obfervations at Botley 
‘Mill and Goudhurf , for determining the length of the degree of 
a great circle, perpendicular to the meridian. 

Since M. Rouguer’s fcale for the degrees of the meridian 
hath been found to agree almoft exa&ly with obferved latitudes 
in this part of the earth, let us take the latitudes of B and R 
(fig. 5.) as they would be found on his fpheroid nearly, and 
apply the pole-ftar obfervations at B and G, in order to find 
the length of the degree of a great circle, perpendicular to 
7 the 


the Trigonometrical Operation , 215 

the meridian of Botley Hill, paffing through GoudhurfL 
We fhall then have PB, the co-latitude of Botley Hill, 
“3 8° 43' iS^.46, and PR, the co-latitude of R, = 38° 53' 
7 y/ .i4. Now, if the latitudes of B and R are nearly true, it 
follows, that the point G mujl be fomewbere in the great circle 
RG, whatever may be its longitude. Therefore the angle BPG, or 
the difference of longitude between B and G, will be found iri . 
the following manner. 

Augment the obferved angle PBG= 119 0 2 T i3 /7 .2, and dimi- 
ni/h the obferved angle PGB = 6o° 1 f 1 by the fame quantity of 
a degree , until PR determined from the triangle BPG becomes zz 
38° 53 ' nearly % which will be when that quantity is f 

2i // . Thus the angles for computation will be ii9°2i / 2 f'.z- 
+ 9 / 2i // =ii9° 30 / 34G2, and 6o° if 1 2i // == 

6o° f 5 4". 7 9 whence the angle RPG, or difference of lon- 
gitude between B and G, will be found = 2 f 36" 75, and the 
arc RG — 1 f 2c/ 7 . 06 nearly = 1 7695 fathoms. And hence the 
degree of a great circle , perpendicular to the meridian , of this 
new fpheroid , will \ m the latitude of R, contain 61248 fathoms 
nearly . 

This follows as a corollary from what hath been already faid ' 
concerning fpheroidical triangles . 

But fince the difference of longitude between B and G was 
formerly determined to be nearly the fame, viz, zf when 

the obferved angles at thefe two Rations, and alfo the latitude 
of B, were fuppofed to be on a figure different from this new” 
ipheroid ; it therefore follows, that the difference of longitude 
between any twofations B and G, difant in the prefent cafe from 
each other twenty-three miles (and they fliould never be much 
ids remote) may be found with fujfcient exadlnefs 7 by having the 

horizontal 


2i 6 Gen . Roy’s Account of 

horizontal angles at each flat ion obferved 'very accurately , and the 
latitude of one of the fiat ions given nearly . 

The difference of longitude between Botley Hill and Goud- 
hurft, found as above, if 3 6 x .7 5 , being augmented by the 
value of the (mail arc comprehended between the meridians of 
Greenwich and Botley Hill = 1" .7, we have ultimately 
2 7 ' ■$<)''• 4*5 for the longitude of Goudhurft, eaftward trom 
Greenwich. 

Art. IX. Difference between obfrved angles on the new fpheroid 

and that of M. Bouguer. 

Laftly, on the fubjeft of thefe companions, let us fee what 
would be the difference between the obferved angles at B andG, 
as determined on the new fpheroid and on that oi M. Bouguer ? 

The latitudes of B and G on M. Bouguer’s fpheroid would 
refpedively be 51 0 \6 / 4i // »54 and 51 0 6" 49' .66 nearly, and 
the angle BPG, or difference of longitude, would ben 27 
26 // .i 8. Now, this laft angle, with the two co-latitudes PB 
and PG, as containing fides, and fuppofed to form a ipherical 
triangle, will give the angles at B and G refpedively 119^ 3 1 / 
26 ".47 and 6o° f .3". 18. But the obferved angles at thefe 
ftations would be 119 0 n / 32A97 and 6o° 16' 5 6 x/ .6 8 , the 
common difference between them being f 53A5, which 
is 32G5 greater than f 1\'\ as was before determined. 
Hence we may conclude, that in this new fpheroid, 
founded immediately on the recent geodetical meafure- 
ments and obfervations of the pole-ftar made at Botley 
Hill and Goudhurft, the verticals from B and G meet the 
earth’s axis at a lefs diftance from each other than they would 
In M. Bouguer’s fpheroid. The length of the vertical is 
ihorter as well as the radius of the parallel, whereby Goud- 
hurft, 


the Trigonometrical Operation. 2 :y 

hurft, or the point R, is lefs removed from the earth’s axis 
than it would be on the former figure ; and confequently it is 
probable, that the fpheroid is lefs oblate. 

From the preceding determinations it is further evident, that 
fuppofing the latitudes of B and G, with the horizontal an- 
gles PPG and PGB to be given by obfervation, not only the 
difference of longitude, or the angle BPG, will be obtained, 
but alfo the arc BR. of the meridian, the arc RG of a great 
circle perpendicular to it, and the oblique arc BG, all con ft- 
dered as arcs of great circles of the fpheroid. 

Art. X. Further illujlratlon of the manner of fettling the lati- 
tudes and longHjtdes of the fations comprehended in the general 
table of refults . 

Having ftiewn, in the preceding part of this fedlion, how 
the length of the degree cf a great circle, perpendicular to the 
meridian, and alfo the differences of latitude and longitude, 
have been obtained by very accurate obfervations of the pole- 
ftar made at certain ftations to the eaftward of Greenwich, 
whereby we have been furnifhed with a fcale for fettling the 
longitudes of all the other ftations where no obfervations of 
the pole-ftar could be had, or only fuch as were not to be de- 
pended upon ; we (hall, by way of further illustration of this 
matter, give another example of the calculations for the point 
M near Dunkirk, which will fuffice for all the other ftations 
comprehended in the general table of refults placed at the end 
of this fedion, where the relpective columns have been filled 
up by the fame or a iimilar mode of computation. 

Let G (Plate X. fig. 8.) be Greenwich ^ GRr its meridian ; 
Gg the perpendicular to that meridian, produced eaftward ; 
MR a parallel to that perpendicular drawn through the point 
Vol. LXXX. F f M; 


2I 8 Gen. Roy’s Account of 

M; and let Mg be a portion of a fmall circle of the fpheroid, 
or parallel to the meridian of Greenwich, produced from M 
northward, until it interfecis the perpendicular in the poiat g. 
Alfo, let MP rep refen t the meridian of the Royal Oufervatory 
at Paris, patting through the point M, and interlecling the pa- 
rallel of Greenwich in P. Further, let C reprefen t the 
church of Notre Dame at Calais, and making, as appears by 

the triangles, an angle RMC of *4° 5 [ ' 3 ' *9 v> i:n ^ ie P a " 
rallel to the perpendicular of the meridian of Greenwich drawn 

through the point M. 

From the annexed general table of the refults of the tri- 
angles, it appears, that MR=gG contains 53804'^ feet = 
89674.7 fathoms; and that GR = gM contains 154938 feet = 
25823 fathoms. Now, fince great circles, perpendicular to 
any meridian of the fpheroid, converge towards each other, 
as they depart from that meridian, in the lame manner as the 
meridians themfelves do in departing from tne equator, but 
by a flower rate, it is obvious, that the perpendicular to the 
meridian of Greenwich, patting through the point M, mutt: 
fall below or to the fouthward of R 011 that meridian, lo as 
that Gr : GR :: rad. : cofine MR = i° 27' 514 conttdered as 
a portion ot a great circle of the fpheroid, perpendicular to 
the meridian of Greenwich. Hence, Gr will contain 2583 1.43 
fathoms = 25' 2 y // .() of latitude, and therefore the latitude of 
r will be 51 0 3' I2".i, audits co-latitude 38° 56' 47A9. Alfo, 
R r meafures 8.43 fathoms, and fubtends an angle RMr = 
19A42. 

In the right-angled fpherical triangle, pole rM, right- 
angled at r, making ufe of the half fum and half difference 
of the containing Tides, r pole and rM, with the co-tan- 
gent 


1 


the Trigonometrical Operation . z { ^ 

gent of 45 0 we have the angle of longitude r 
pole M, . . . . ^ 2 i j 42 5 

The angle, pole Mr, ~88 u 214 

And the complement of this laft, or the con- 
vergence of the meridian of M (fuppofed to co- 
incide with that of Paris) to the meridian of 

Greenwich, ^ 1 48 38.6 

Alfo, as fine 88° 1 T 2i 77 . 4 : fine 38 s $ 6 ' 47 // . 9 rad. : fine 
38° 5s 7 1 1 7/ * 2 the co-latitude or M; whence its latitude be- 
comes 51 0 I 7 4 8 /7 .8, from which, deduding the fpheroidical 
corredion o /7 .5, we have the true latitude of Mz=z$i° T 4 8 /7 .^ 
The difference between this and the latitude of 51 0 3' i 2 \i 
will be i 7 23 77 .8, anfwering on the fpheroid to 1416.77 fathoms ; 
and this laft number being added to the value of the arc Gr = 
2583 1 *43 fathoms, we have 27248.2 fathoms for MP, or the 
diftance of the parallels of Greenwich and M on this new 
fpheroid. 

Laftly, if to this mean diftance of the parallel of M from 
Greenwich, we add the mean diftance of the parallel of M 
from Paris = 1 33398.8 fathoms, we (hall then have 160647 
fathoms for the mean diftance of the parallels of Greenwich 
and Paris, anfwering to the celeftial arc of 2 0 38" z 6 '\ 
Hence the mean degree of the meridian between Greenwich 
and Paris correfpondmg to the latitude of 30° 9 / f, contains^ 
60638.3 fathoms, or about ij fathom lefs than M. Bouguer’s 
degree for the fame latitude. 


F f 2 Art. 


1 


220 


Gen . Roy’s Account of 


Art. XI. Comparifon of the angle between the meridian of 
the point M and a line drawn from thence to Calais, as 
approximately deduced from the Brit if and French obfer - 
various. 

In the fpneroidical quadrilateral GgrM (fig. 8.), formed by 
three arcs of three great circles, and one of a fmall circle of the 
fpheroid, we have two right angles at G and r, and two others 
at g and M, each greater than a right angle by 5G.7 ; there- 
fore the angle RMC, refuiting from the triangles = 14 5 d 

— RMr (1 p /7 .4 2 ) ~ 1 4 ° 5° 7 44 "-S+ 9 °° q/ 9 "'7 ( CM <?) = 
104° 50' 54 y/ .*2, is the angle ^MC, or that which Calais makes 
with a parallel to the meridian of Greenwich drawn through 
the --point M. From this laft angle fubtradting the angle PM g 
= i° 48' 38G6, or the quantity by which the meridian of M 
(fuppofed to co incide with that of Paris) converges towards 
that of Greenwich, there remains the angle PMC =103 2 7 
ic".6 for the angle that the meridian of M fhould make with 
a line drawn from D, or Dunkirk, through that point to Ca- 
lais, according to the Britifh obfervations. 

By the late French operations, the meridian of Dunkirk 
makes, with a line drawn through M to Calais, an angle of 
102 0 59 7 51 // «5'. The convergence of the meridian of M to 
that of Dunkirk, on a difference of longitude of 2 / 21^.54, 
is l 7 49 /7 .94, which being added to 102° 59' 51 7/ .-5, we have 
1 03° i 7 4i // .44 for the angle that the meridian of M, or of 
Paris, makes with a line drawn from Dunkirk through that 
point to Calais. The difference between the two refults 34 7 / .i6 

is nearly equal to the mean of two extremes f — -g ) = 37" is 

the apparent uncertainty, in the determination of that angle 

is by 


the Trigonometrical Operation. 22 r 

by two fets of angles given in the Meridienne venfee, as adverted 
to in the Paper of 1787, Phil.Tranf. Vol. LXXVII. p. 195, 196. 

Art. XII. The longitudes of Dunkirk and Paris , eafward from 
Greenwich , determined by the fum of four differences of me- 
ridians. 

In fig. 9. let PA be the meridian of Greenwich ; G Goud- 
hurft, PR its meridian ; T the Ration at FolkRone Turnpike, 
PS its meridian ; C Calais, PC its meridian ; D Dun- 
kirk, and PB its meridian. Alfo, let AG, RT, SC, and BC, be 
arcs of great circles, making the angles PAG, PRT, PSC, 
and PBC, right ones. 

The angle at GoudhurR, between its meridian and Tenter- 
den, is 107 26 40 .3 > hence, by drawing parallels to this 
meridian through Tenterden and the Ration at Allington Knoll 
(fee the plan of the triangles) we fliall get 946.6 fathoms for 
what the Ration at the Turnpike is fouthward, and 28098.8 fa- 
thoms for what it is eaflward from the meridian of GoudhurR. 
Now, 60859.4 fathoms being nearly = T of the meridian in the 
latitude of GoudhurR, we have 946.6 fathoms = 56" nearly za 
the arc GR; and the latitude of GoudhurR being 51° 6' 49 // .'6 s 
that of the point R is 51° 5' 53". 6 ; hence the co-latitude RP 
= 38 54‘ ! 6 // .4: and fince the degree of a great circle, per- 
pendicular to the meridian, in this latitude has been fhewn to 
contain 61248 fathoms nearly; therefore RT= 28098.8 fa- 
thoms will be 27' 31 // . 6 . This arc and RP give the angle 
RPS = o° 43' 49C86 for the difference between the meridians of 
GoudhurR and FolkRone Turnpike. 

The angle at FolkRone Turnpike between its meridian and 
Dover was obferved 66° 48' 35", and if we draw a parallel to 
this meridian through Dover, we fhall find, that Calais is 

25284.2 


222 Gen. Roy’s Account of 

25284.2 fathoms eaftward from the meridian of the Turnpike. 
Now, the latitude of Calais being 50 57' 30 // nearly (which 
is accurate enough for computation) the length ot the degree 
of a great circle, perpendicular to the meridian in that latitude, 
will be 6:246 fathoms nearly. Hence, 25284.2 fathoms = 
24' 46".8 = the arc CS ; this, with the co-latitude CP (39" 2' 
30"), give the angle CPS = 39' 19". 48, for the difference of 
longitude between the Turnpike and Calais. 

By Comte de Cassini’s Paper, communicated in January 
1789, it appears, that the angle at Dunkirk, between its me- 
ridian and Broulezele, is io° 18' 25" ; and that between Broule- 
zele and Calais 66" 41' 46"!, the fum is 77 o' w '\ for the 
angle at Dunkirk, between its meridian and Calais. In the 
fame Paper we have 19349 34 toifes for the diftance of Dun- 
kirk from Calais; this, with the angle 77 o 1 1 "{, give 
18853.7 toifes or 20093.3 fathoms for the diftance of Calais 
weftward from the meridian of Dunkirk, which, by taking 
61246 fathoms=i° (that of a great circle perpendicular to 
the meridian in the latitude of Calais), is equal to 19 4 1 
=thearcBC; and this arc, with CP the co-latitude of Ca- 
lais, give the angle CPB=3i' I5".H for the difference be- 
tween the meridians of Calais and Dunkirk. 

The angle APR, or the difference of the me- 
ridians of Greeenwich and Goudhurft, has al- 
ready been found (fee the end of the 8th article, 0 , u 

and alfo the table of general refults). 


The angles 


RPS 
SPC 
■ CPB 


= 0 
= 0 


27 39-45 
43 49.86 
= 0 39 19.48. 
= 0 31 1 5. 1 1 


Hence the total angle APB, or long, of Dunkirk, is = 2 22 


A* 


It 


the Trigonometrical Operation. 22 ,, 

It bath been already remarked, that, from p. 276. Meri. 
dienne lerifiee, Dunkirk is 1430 toifes eaft ward from the me- 
ridian of- Paris; and that in p. 36. of the Defection Geome- 
trique de la France, we find it only 1416 toifes. Now, thefe 
will give 2' 22 // .6 and 2' 2i".a refpeftively for the difference 
of meridians of Dunkirk and Paris; the mean is 2' 21". 9 for 
the longitude of Dunkirk eaft from Paris ; therefore 2 0 22' 

3 -9 ~ 2 21 / -9 = 2 19' 42 // , or 9' 18A8 in time, will be the 
longitude of Paris eaft from Greenwich nearly. 

Again, in fig. 10. let P be the pole ; G Greenwich, PW its 
meridian ; RD an arc of a great circle making the angle at R 
a right one, and pafting through D ; and DW an arc of the 
parallel of latitude of Dunkirk. 

By p. 240. of the Man., de V Acad. 1758, the celeftial arc 
between Paris and the ftation of the feftor near Dunkirk is 
2°u' 50"; to which adding 5 ". 3 (-844 toifes) for what 
the tower is north from the ftation, we have 2 0 iff 55A3 for 
the arc between Paris and Dunkirk ; therefore, if the latitude 
of Paris is 48° 50' 1 4.", that of Dunkirk will be 51 0 2' 9". 2, 
whence its co-latitude becomes 38° 57'' 50 // .7 = DP. 

From what has been faid concerning fpheroidical triangles, 
it follows, by way of corollary, that to find RD by fpherical 
computation, when DP and the angle at P are given, it is 
neceffary to diminifti DP by a certain quantity determinable 
from the nature of the fpheroid ; this quantity is about 0".$ 
when the fpheroid is M. Bouguer’s; therefore DP may be 

taken = 38° 57' 50 x/ .2, which is fufficiently accurate for com- 
putation. 

Hence, as rad. : fine DP :: fine 2 0 22' $".9 - WPD : fine 
1 29 19 / . 1 7 = the arc DR. Now, 61247 fathoms being 
equal to i° of a great circle perpendicular to the meridian in 

the 


22 a Gen. Roy’s Account of . 

the latitude of Dunkirk nearly, we have, as T : 61247 :: 

e° 1 o''. 1 7 : 9 1 j 75.3 fathoms = the arc DR. 

But the length of this arc DR has been found nearly the 
fame, that is, 91176.3 fathoms (fee the table of general re- 
fults) by continually drawing parallels to the meridian of 
Greenwich through the different Rations between it and Dun- 
kirk 5 therefore, although that method in general is not Briefly 
accurate, having a tendency to give the relults in excels; yet 
it is evident, that the length of the arc of a great circle lo 
determined will differ very little from the truth, when the 
ieries of triangles employed for that purpofe are contiguous to 
it, and follow its diredtion nearly. 

Art. XIII. For the dijlance between the parallels of latitude of 

Greenwich and Paris. 

The diftance between the parallels of Greenwich and Paris 
has already been determined in Art. X. of this fedtion, by 
taking M (1420.41 toifes weftward from Dunkirk) as the in- 
termediate point. Let us next fee what will be the reiult when 
Dunkirk is made ufe of inftead of M ? 

In fig. 10. as cof. RD : rad. cof. DP : cof. PR=38 56' 
24^.07 ; but DP by obfervation is = 38' 57' 50 // .7 = PW; 

hence PW-PR = 38’ 57' S°"- 7 ~ 3 ^ 5 6 ' ^".oy = i' 26 '.63 
— RW — 1464.5 fathoms nearly, by taking 60858 fathoms for 
a degree of the meridian, that being nearly its value in the 
latitude of Dunkirk. 

By our operation Dunkirk is 25425 fathoms fouthward from 
Greenwich ; but the great circle DR meets the meridian of 
Greenwich about 8§ fathoms further fouth, that is to fay, GR 
is 25425 + 8.5 =; 25433.5 fathoms, which being added to 1 464.5 

gives 


the Trigonometrical Operation . 2 2 5 

gives 26898 for the diftance between the parallels of latitude 
of Greenwich and Dunkirk. 

Because Dunkirk is fituated near the meridian of Paris, the 
diftance between the parallels of latitude of thefe places will be 
nearly equal to what Dunkirk is north from Paris, namely, 
1255173, or 125495 toifes (fee the pages formerly quoted). 
Thefe numbers give respectively 133770 + 26898 ~ 1 60668, 
and 133746.3 + 26898 = 160644,3 fathoms for the diftances 
between the parallels of Greenwich and Paris, a mean between 
which will nearly be 160656 fathoms. 

If therefore the celeftial arc of the meridian between Green- 
wich and Paris is 2° 38' 26", we get 60846 J or 60837 § fa- 
thoms for a degree of the meridian in latitude 50 0 g'f , the 
middle point between Greenwich and Paris ; and a mean of 

* 

thefe two refults 60841 f only exceeds M. Bouguer’s degree 
for the fame latitude about 1 J fathom, a quantity not differing 
fenfibly from the defedf that was brought out by the compu- 
tation in Art. X. Finally, therefore, by taking a mean be- 
tween this and the former length 608385 , wefhall have 60840 
fathoms for the degree of the meridian in latitude 50° f 2 j''\ 
agreeing almoft: exactly with that of M. Bouguer. 

Art. XIV. Comparifon of the length of a degree of a great circle , 
perpendicular to the meridian in Kent , with that in the South 
of France . 

M. Cassini de Thury, in his Book Fa Meridienne neerifee , 
has given us the detail of an operation carried on in the South 
of France in latitude 43 0 32% for the determination of the 
length of a degree of longitude, by marking, at the extremi- 
ties of a long and well afcertained diftance, the inftantaneous 
explofion of gunpowder in the open air. For this purpofe a 
Vol. LXXX. G g Series 


226 <j en. Roy’s Account of 

feries of triangles was extended along the ffiore of the Medi- 
terranean Sea, between Cette and St. Vi&oire, the extreme 
ftations from whence the light was repeatedly obferved, ns 
fired at the church of St. Maries, nearly in a central fituation, 
at the mouth of the lefler branch of the river Rhone. 

From the refult of this operation, the beft of the kind that 
has ever been executed in any country, it appears, that a degree 
of longitude in that latitude meafures 44355.7 fathoms; 
whence it follows, that the degree of a great circle, perpendicular 
to the meridian there, muff contain 61182} fathoms, being 
65} fathoms lefs than the degree in the middle of Kent, lati- 
tude 5 1° 6 7 50". 

Now, if we compare this difference with that found between 
the correfponding degrees of great circles for the fame latitudes 
on M. Bouguer’s hypothesis, we Shall find them perfectly 
confiflent with each other in their rate of diminution : for, by 
con Suiting the table, it will be feen, 'that this degree in lati- 
tude 51 0 6 7 5c/ 7 exceeds that in latitude 43 0 32' by 64.7 fa- 
thoms, agreeing within lefs than a fathom with the former 
difference. 

On due confederation of fo many corroborating circum- 
stances as have been adduced in the courfe of this fe&ion, 
there feems, therefore, to be Sufficient room to conclude, that 
the earth differs but little either in its figure or dimenfions from 
what hath been affigned to it by M. Bouguer. It is true, in- 
deed, that a new fpheroid has been here prefented, Somewhat 
lefs flat than the former, founded immediately on the Britifh 
observations ; and thefe being again compared with the refult 
of the above-mentioned operation, whereby the degree of lon- 
gitude in the South of France was determined, it is from the 
combination of both refults that the annexed table of the 

lengths 


the 'Trigonometrical Operation . 2 zy 

lengths of degrees of great circles and of longitude has been 
conftru£ted for middle latitudes only, extending from 42 0 to 
52°, Without the help of fuch a table, the new longitudes of 
fome intermediate places, which we fhall have occafion here- 
after to compare with the old, could not have been fo accu- 
rately computed as was wifhed. Now, although it is be- 
lieved, that this table will be found to anfwer nearly in that 
zone of the earth for which it is intended ; yet it is only 
offered for temporary ufe, until future obfervations of the pole- 
liar in the fame parallel, but on longer diftances than our recent 
feries of triangles afforded, or the extenfion of operations of 
the fame nature with ours into remoter latitudes, fhall have 
furnilhed data for one more correft. 


Table of the degrees of great circles and of longitude for 

middle latitudes. 


Places. 

Latitudes. 

Deg. of great cir- 
cles, perp. to the 
meridian in fath. 

Degrees of longitude 
in fathoms. 


0 

/ 

// 



Diff. 



Diff. 


4a 

0 

0 

61 170.5 

1 

h 0 

45458-5 

1 



43 

0 

0 

61178. 

I 

7*5 

44742.8 

1 

7 * 5-7 

South of France 

43 

32 

0 

61182.5 

} 

4*5 

44355-7 

} 

387.1 


44 

0 

0 

61186.5 

} 

4 - 

44013.9 

} 

341.8 


45 

0 

0 

61195. 

} 

8-5 

4327 I -4 

} 

742-5 


46 

0 

0 

61203. 

} 

8. 

42515-2 

} 

756.2 


47 

0 

0 

6x211.5 

} 

8-5 

4 X 746 >I 

} 

769.1 


48 

0 

0 

61220. 

} 

8-5 

4O964.2 

} 

781.9 

Paris Royal Obfervatory 

48 

5° 

14 

6x227.5 

} 

7-5 

40303.2 

} 

662.0 


49 

0 

0 

6x229, 

} 

I *5 

4OI69.8 

} 

j 32.4 


50 

0 

0 

61237.5 

} 

8-5 

39362.8 

} 

807.0 


5 1 

0 

0 

61246.5 

} 

9 - 

3 8 542.7 

} 

820.1 

M near Dunkirk 

5 1 

1 

48-3 

61246.7 

} 

0.2 

38518.8 

} 

23-9 

Dunkirk 

5 * 

2 

9-3 

61246.75 

} 

0.05 

385*4-1 

} 

4 7 

Middle of Kent 

5 1 

6 

49.6 

61248. 

} 

1.25 

38450.0 

} 

64. 1 

Greenwich Royal Obferv. 

5* 

28 

40 

612511 

} 

31 i 

38148.7 

} 

3 OI -3 


52 

0 

0 

61255. 

} 

3-9 1 

37712.3 

} 

436.4 


Gg 2 


Art, 


228 


Gen . Roy’s Account of 


Art. XV. Comparifon of the old longitudes of fame places on the 
Jkirts of the kingdom of France with what they will be when 

computed by the new data. 

If the preceding determinations of the longitudes of the 
feveral Rations between Greenwich and Dunkirk are accurate, 
or nearly fo } as founded immediately on the Bntifh oufeiva* 
tions, and ultimately combined with the refult of the opera- 
tion in. latitude 43 0 32% it follows, that all the longitudes of 
the great map of France, the labour of more than half a 
century, will be confiderably affedted thereby, in proportion 
to the diftances of the places, eaftward or weft ward, fiom the 
meridian of the Royal Obfervatory at Paris refpeclively. 

To fhew the effedf produced by the new data , we. fhall col- 
lect, in the following table, the latitudes and old longitudes of 
a few noted places on the Ikirts of that great kingdom, and 
annex to them the new longitudes refulting from computations 
made with new lengths of degrees of great circles, perpendi- 
cular to the meridian, correfponding to their latitudes reflec- 
tively. It will readily be conceived, that the objedt here in 
view is folely this ; namely,' that aftronomers who live near thofe 
places, and who have their time, that is to lay, the directions 
of their meridians very accurately afcertained, may, by their 
future correfponding obfervations (which fhould only be occul- 
tations of the fixed ftars behind the moon’s dark limb) com- 
pare the old with the new longitude, and thus be enabled to 
fatisfy the curious world, which of the two comes neareft 
to the tfuth. 


Com- 


Weft from Paris, } Eaft from Paris 


the 'Trigonometrical Operation. 


ZZ<) 


Comparative table of the old and new longitudes of fome noted places 

on the lkirts of the kingdom of France. 


Places. 

Latitudes. 

Longitudes, 

1 

DifF. of old and new long. « 

Old 

New. 

in deg s &c. 

in time. 


O 

$ 

✓ 

// 

0 

/ 

// 

0 

/ 

// 

/ 

// 

Sec. 

Thirds. 

Wilier de Cette 

43 

24 

6 

I 

21 

7 

I 

20 

37 

O 

23 

I 

32 

Tour de Planier, near Marfeilles 

43 

1 1 

58 

2 

54 

8 

2 

53 

6 

I 

2 

4 

8 

Signal of St. Vi£toire 

43 

3 i 

52 

3 

i 5 

8 

3 

l 3 

58 

I 

10 

4 

40 

i Strafbourg (Conn, de T. 1788) 

4 b 

34 

35 

5 

26 

18 

> 

24 

6 

2 

12 

8 

48 

j Ditto (Defcrip. Geomet. 1783, 

48 













L p. 1 7 1 • 

34 

5 ° 

5 

25 

0 

r* 

3 

2 3 

33 

I 

27 

5 

48 

Tour de Cordouan at the mouth of 














the Garonne, Conn, de T. 1788 

45 

35 

15 

3 

30 

38 

3 

29 

18 

I 

20 

5 

20 

.J St. Malo .... 

43 

39 

0 

4 

22 

22 

4 

20 

37 

I 

45 

7 

0 

Fort du Pilier, at the mouth of the 














Loire .... 

4 7 

2 

29 

4 

42 

20 

4 

40 

3 ° 

I 

50 

7 

20 

^Ulhant Light-houfe 

48 

28 

3 ° 

7 

24 

33 

7 

21 

4 1 

2 

52 

1 1 

28 

The greateft difference between Strafbourg and Uftiant 
The leaft difference . 

The mean difference 

• 

• 

• 


5 

4 

4 

4 

J 9 

4*2 

20 16 

17 36 

18 46 


With regard to the longitudes in the preceding table, it is 
only neceffary to obferve, that the two books of 1744 and 
1783, fo often quoted, are not always confident with each 
other, and both do fometimes difagree with what has been 
placed on the margin of the map of France. It would feem, 
that in the Defcription Geometrique a fcale for degrees of lon- 
gitude has been ufed confiderably greater than that correfpond- 
ing with the fpherical hypothefis adhered to in the conftruc- 
tion of the map, yet dill too fmall for what we have found 
to be their meafure in Kent, or that refulting from their own 
operations in the South of France. But if a fimilar mode to 
that which they pradtifed with lo much fuccefs in the South 

had- 


2 2o Gen. Roy’s Account of 

had been employed in the North of France, the fame fort of 
refult as we have obtained in Kent would probably have been 
the confequence ; in which cafe it cannot be doubted, that the 
fpherical hypothefis would have been entirely reje&ed, and their 
lengths of degrees of longitude would have been fuited to an 
oblate fpheroid, whofe degrees of the meridian and of great 
circles perpendicular to it had nearly the proportion to each 
other of 60840 to 61239 for the middle latitude between 
Greenwich and Paris, being an excefs of 399 fathoms on each 
degree in the longitudinal dire&ion. 

On the whole, therefore, as matters ftand at prefent, it is 
fufficiently obvious, that, in the total extent of the kingdom of 
France from Strafbourg on the eaft to Ufnant on the weft, the 
difference between the old and new longitude amounts to be- 
tween 1 7 and 20 feconds of time ; that is to fay, the real dif- 
ference between the meridians of thofe places, it is prefumed, 
will not be found by future obfervations made on the occultations 
of the fixed ftars, to be fo great as it was formerly fuppofed to 
be by that quantity, or fomething approaching it very nearly. 


Art. XVI. The obfervations of eclipfes cannot be depended upon 
for determining •with fufficient accuracy the difference of longi- 
tude in vicinal ftuattons. 

/ - ^ m 

Finally* with regard to differences of longitude, it may not 

be improper in this place to remark, that, in vicinal lituations, 
fuch as Greenwich and Paris, the eclipfes of the fun and 
moon and Jupiter’s fatellites do not, in general*, give refults 

* The refult deduced by the ProfelTor Piazzi, of the Univerfity of Palermo, 
from the obfervations of the eclipfe of the fun on the 3d of June, 1788, made 
at Greenwich, in company with Dr. Maskelyne and M. d’Arqjiier, as given 
in the Phil. Tranf. for 1789, p. 58. is an exception well worthy of notice. 


the Trigonometrical Operation . 2 gt 

fufficiently near the truth to deferve even the name of an ap- 
proximation. This will inconteftably appear by comparing 
the agronomical refult produced in that way with ours ob- 
tained by actual meafurement on the furface of the earth, and 
angular obfervations of the pole-ftar. Thus, by taking a 
mean of a multitude of the beft of thefe obfervations of 
eclipfes, &c. collected and corrected with great care for the 
purpofe, the difference in time between Greenwich and Paris 
amounts to 9' 30^! *, iilftead of being only 9' 19" nearly, 
which our operation makes it. Now, if the difference in time 
between thefe two Royal Obfervatories was really fomuch, the 
degree of a great circle perpendicular to the meridian in thefe 
latitudes (51° 6 ' 50" that of Goudhurft, or 51 0 T 48^ that of 
the point M, it matters little which of the two is taken) 
would be between 1200 and 1300 fathoms fiiorter than the 
degree of the meridian in the fame latitudes. Hence the 
earth, inftead of being an oblate fpheroid confiderably 
tened at the poles, would be one extremely prolate, in propor- 
tion with regard to the former figure of more than three to 
one, or between 1200 and 1300 — to about 400 + . 

In remote fituations^ fuch as Europe and America, Europe 
and the eaftern parts of Afia, feparated from each other by 
wide oceans, the differences of longitude can only be obtained 
by means of aftronomical obfervations. And as thefe will 
always be liable to fome error, which may be as great on a 
difference of one or two, or a few degrees, as on the whole 
180% it is fufficiently obvious that, to render the effed: of fuch 

* From Dr. Maskelyne’s Paper of 1787, Phil. Tranf. p. 183. it appears, 
that the eclipfes of the ifl Satellite of Jupiter give immediately for the difference 
of meridians of the two Obfervatories (p without being combined with 

obfervations made in other parts of Paris. 


error 


2^2 Gen. Roy’s Account of 

error as fmall as poflible, occuitations of fixed ftars fhould only 
be made ufe of, for obtaining conclufive determinations. 

In vicinal fituations, the next beft mode to angular mea- 
furement is no doubt that of marking, by means of well- 
regulated clocks, as was done in the South of France, the 
repeated inftantaneous explofion of light, obferved at ftations as 
far diftant to the eaftward and weftward of the place of explo- 
fion as the circumftances will permit in practice, thefe diftances 
having been for the purpofe accurately fettled by trigonome- 
trical operation. The preferable ftations for experiments of 
this fort will be pointed out in the conclufion to the prefent 
Memoir. 


Table 




For corre&ing the TABLE in the Paper of 1787 


[To follow the Table of General Results, page 231. 


f Greenwich Rl. Ob. 

1 { Perpignan 

Greenwich and M 
r Point M near Dunkirk 

2 { Perpignan 

Point M and Paris - 
T Paris Rl. Ob. 

8 1 Perpignan 

Paris and Bourges 
f Bourges 

4 1 Perpignan 

Bourges and Rodes 
J Rodes - - 

* ' Perpienan 

O 

' !" 


T 

// 

/// 

O 

Pts. 






















'5 1 
42 
MP 
5 1 
42 

48 

42 

2840 

4 i 52 

149 
41 52 

5014 

4152 

00 

00 

8 

00 

00 

00 

} 8 |« 6 
difF. 0:26 

I 1 

} 819 
diff. 2 1 1 

j 6 8 

diff- 1 45 

} 423 

diff. 2 43 

1 1 
| *39 

48 

S° 

S7 

35 

22 

9 

12 

5* 

21 

00 

S2 

8 

8 

00 

*9 

41 

5 

36 

8. 

0. 
8. 
2. 
6. 

1. 

4- 

2. 
1. 

78 

4475 

3325 

*93* 

1394 

7525 

3869 

6309 

656 

506687 
1 33409 
373278 
106612 
266666 
165961 
100705 

534343- 

27235. 

507108. 

*33467. 

373641. 

106658. 

266983. 

166200. 

100783. 

ei 

SO 

+ 5 2I ')t 
+ S 8 J 

+ 363 g 

+ 46 j- g 

+3*7 \ a 
+ 239I a 

+ 78 J | 

535848 . 

27342. 

508506. 

133957 . 

374549 - 

106989. 

267560. 

166599. 

100961. 

+ 1819. 

+ 5 8 4 

-M27I A 

+ 377 r ~ 
+ 894 ” 

+ 638 
+ 256 J 

535758 . 

27337 - 

508421. 

133932. 

374489. 

106971. 

267518. 

166572. 

100946. 

+ * 734 -) 

+ 523I 
+ 1211 I 

+ 359 ^? 

+ s 4 ; 

+ 6n j 
+ 241 

535024. 

27294. 

507730. 

* 33732 - 

37399 s - 

106820. 

267178. 

*66354- 

100824. 

4 10 43 
+ 3 2 3 
+ 720 £. 
4- 208 +1 

tN 

+ 5*2 “ 

+ 393 

+ *37 

534909 . 

27288. 

507621. 

133700. 

37 39 2 *'- 
106796. 
267125 
166320. 
100805. 

+ 934 -j 
+ 29 * I 

+ 643 ° 

+ T; 

+ 459 1 
+ 359 J 
+ 100 

533880 . 

27234.’ 

506646. 
* 33440 . 
373206. 
106590. 
266616. 
1 66002. 
100614. 

~ 72 U 

+ 4 * ] 
-91 

5338 oi. 

27224- 

506577. 

I 33398 - 

373 * 79 - 

106569. 

266610. 

165990. 

100620. 

-110 

- 11 

- 99 „ 

- 43 r « 

- 56 ' 

+ 29 - 

- 85J 

533734 - 

27212. 

506522. 

* 33354 - 

373*68. 

106549. 

266619 

165986. 

100633. 

-*65 

— 55 I 

— 1 10 1 00 

, 1 ^ 

- 47 [ 

+ 25 | 

— 72 * 

534928 . 

27288. 

507640. 

*33705 

373935 - 

106796. 

267139. 

*66335. 

100804. 

+ 953 ' 
+ 296 
+ 657 
+ 184 
+ 473 
+ 374 
+ 99 - 

r» 

PO 

r HH 

HH 

+ 

533652-4 

27234. 

506418.4 
* 334 * 6-5 
373OOI.9 
*06550.4 

266451.5 

165908.5 
IOO543. 

—268.6 1 

+ 7-5 
-276.1 £ 

— 61.6 )■ $. 

-214.5 1 

— 52.5 

— 162. 

47 

42 

s 1 4 

4152 

1 

41 

00 

44 

42 

21 n 

4152 

3 6 

00 


t 


Obferved Celeftial Arc of the Meridian between Greenwich and 
Perpignan. 

Meaf d 

Terrel 1 

Arc. 

Computed Terreftrial Arc of the Meridian between Geenwich and Perpignan. 

on a Sphere. 

on different Ellipfoids. 

on different Spheroids. 

f Greenwich Rl. Ob. - 

1 \ Tower of Dunkirk . 
f T ower of Dunkirk - 

2 L Paris RL Ob. 

J Paris RL Ob. 

8 [Tower of Bourges 
J Tower of 'ourges 

4 [N. D. at Rodc-s 
J N. D. at Rodes 

5 [ St. Jaumes at Perpignan 

Latitudes. 

Differences. 


Semidiam. 

3486975. 

iftR.S.D. 

r 179.047. to 
1 178-047 

2d.RS.D. 

f 192.483 to 
1 1 91.483 

3dR.S.D. 

J2 16.06 to 
[215.06 

.fthR.S.D 

f 222.55 t0 5 th R - S. D. 

1 22I ->5 | 

f 230. to 
I229. 

6th R. S. D. 

1310.31° 
1 3°9-3 

7th R. S. D. 

( 540. to 
1 539 

ill R. S. D. 

f 222.55 to 
1 22 1.55 

id R. S. D. 

f 179.410 

1 178.4 

O / // 

51. 28. 40. 

51. 2. 9.3 

48. 50. 14. 

47- 5- 2.6 

44- 21. 2.4 
42. 41. 56. 

O 11 / 

} 0. 26. 30.7 

} 2. 11. 55.3 

} 1. 45. 1 1.4 

j 2. 44. 0.2 

} I- 39* 6.4 

Fath’ 

26898 

*337.58 

106647 

166115 

100448 

Fath* 

26891 

*33811 

106696 

166352 

100526 

- 7 
+ 53 
+ 49 
+ 237 

+ 78 

Fath s 

27000 

134299 
10 7024 
166753 
100704 

+ 102 
+ 54* 
+ 377 
+ 638 
+ 256 

Fath’ 

26995 

*34274 

107006 

166727 

100689 

+ 97 
+ 5*6 
+ 359 
+ 612 

+ 241 

Fath s 

26953 

134073 

106847 

166516 

100567 

+ 55 
+ 3*5 

+ 200 

+ 401 
+ J*9 

Fath’ 

26946 

134042 

106831 

166474 

100548 

+ 48 
+ 284 
+ 184 

+ 359 
+ 100 

F ath s 
26893 

133782 

106625 

166156 

100358 

- 5 
+ 24 

-22 
+ 4* 
-90 

Fath’ 

26883 

*33739 

106604 

166144 

100364 

- *5 

- 19 

- 43 
+ 29 

-84 

Fath 

26872 

133695 

106584 

166140 

100377 

- 26 

- 63 

- 63 
+ 25 

- 71 

Fath s 

26946 

134047 

106831 

166489 

100547 

+ 48 

+ 289 
+ 184 
+ 374 
+ 99 

Fath* 

26893 

*33758 

106585 

166062 

100287 

- s 

0 

- 62 

- 62 
— 161 

Greenwich & Perpignan] 

8. 46. 44. 

533866 

534 2 76 

+ 410 

535780 

+ 19*4 

53S 6 9* 

+ 1825 

53+956 

+ 1090 

534841 

+ 975 

5338*4 

-52 

533734 

-13*' 

532668 

-195 

534860 

+ 994 

533585 

— 281 


The meafured Arc between Paris and Dunkirk is taken a Mean between 125517! and 125495 Toifes, or 133770 and 133746 Fathoms. See Se£L VI. Art. xii. 

The Latitudes of Dunkirk, Bourges, Rodes, and Perpignan, are deduced from the Celeftial Arcs given by M. de la Caille, in pag. 240, 241, Mem. dc t Acad. 1758, and making the proper Redu&ions for the Diftances of the Stations 
M'crid. virifiie. 


of the Seftor at each Place, as given in the 

SECTION 





[To face page 2:32 ] 


Table containing the General Results of the Trigonometrical Operation.. 







By Plane Trigonometry. 









Stations. 


Diftances 

in Feet. 

Bearing or 


Direft Dift. 


Longitude. 

Vertical Heights. 





from the Metid. 
of Greenwich. 

from the Perp. 
to the Merid. 

Angle with the" 
Meridian. 

from 

Greenwich. 

Latitude. 

in Degrees, &c. 

in Time. 

Ground 
above the Sea. 

Telefcope 
above Ground. 

Total. 


Greenwich R. Ob. Tranfit Room 



24603.86 

O J // 


Feet. 


O 111 

m. s. th. 

beet. 

170.5 

feet. 

43-5 

Feet. 

214 

f 

Norwood - “ 

- 

19306.54 

38. 7.16 

SW 

31274.48 

5 i . 24 - 37"34 

0. 5. 2.4 

0.20. 9.6 

380.3 

9.2 

389-5 

1 

Hundred Acres 

- 

43333-9 

5 ° 937-9 

40.23.18.5 

sw 

66876.73 

51. 20.17. 3 

0. 1 1. 19.5 

0.45.18. 

433-8 

9.2 

443 

Weft from j 

Hanger Hill Tower 

- 

67740.69 

16729.21 

76. 7.40.2 

NW 

69775.8 

51.31. 24.16 

0.17 46 5 

1. 11. 6. 

- 21.3. 

38 . 

251 

Greenwich i 

1 

Hampton Poor-houfe 

King’s Arbour ... 

- 

83086.16 

18537.98 

77.25.20.3 

sw 

85129.1 

S 1 - 2 S - 3 S - 2 

0.21.45.3 

I.27. 1.2 

63-5 

37-5 

101 

- 

102264.55 

1037.69 

89.25. 7.7 

N W 

102269.8 

51.28 47.16 

0 26.48.5 

1.47.14. 

94.8 

37-5 

132.3 

l 

St. Ann’s Hill - 

Wardrobe Tower of Windfor Caftle 

- 

119404.04 

I 37 °S°-S+ 

288C2.77 

2562.72 

76.24.55.7 

88.55.43.5 

sw 

NW 

122840.6 

i 37074-5 

51.23.51.4 

51.28.59.7 

0.31.14.7 
0.35 5 S. 8 

2. 4-58-8 
2.23.43.2 

3 21 3 

20.7 

34 2 

f 

Rotlev Hill 


171.6 

72882.5 

0. 8. 5.6 

SE 

72882.7 

si. 16.41. 54 

0. 0 2.7 

0. 0.10.8 

859-3 

20.7 

8S0 


Severndroog Caftle on Shooter’s Hill 

- 

14032.3 

4069.8 

73 - 49-34 

SE 

14610.58 

5 J .27 59-8 

0. 3 40.65 

0.14.42.6 

417-8 

64.2 

482 


Frant - - 

- 

62342.5 

138460.4 

24.14.23.6 

SE 

151848.2 

51. 5 - 53-9 

0.16.12.5 

1. 4-50. 

604.1 

54-9 

659 


Wrotham Hill ... 

- 

71850.3 

593 ° 5 - 8 

50.27.48.5 

SE 

93164.6 

51.18.53.86 

0.19.12.3 

1-.16.49. 2 

761.8 

9.2 

77 i 

I 

Goudhurft - 

- 

106342.5 

.132592. 

38.43.50- 1 

SE 

169968.8 

51. 6.49 62 

0.27.39-45 

1.50.37.8 

437-9 

59 1 

497 


Fairlight Down 

- 

143308.1 

21861 1.6 

33.14.46.8 

SE 

261396.7 

50.52.38.84 

° 37 - 5 - 

2.28.20. 

539-5 

5-5 

599 


Hollingborn Hill 

- 

151078.1 

77077.6 

62.58.12.2 

SE 

169604.1 

51.15.53-5 

0.39.25.2 

2 37.40.8 

6l I 

5-5 

.616.5 


Tenterden — 

- 

158317-6 

148567. 

46.49.11.4 

SE 

217109.7 

51. 4. 8.15 

0.41. 8.15 

2 - 44 - 3 2 - 6 

220.6 

101.7 

322.3 


Ruckinge - 

- 

204801.6 

149410.3 


SE 

2535096 

5 '- 3-54 9 

0 53. ‘2.6 

3 - 3 2 - 5°-4 

3*9 

5-5 

37-4 

Eaft from 
Greenwich 

Lvdd 

- 

2 ° 9339-3 

190695.6 

47.40.6 

SE 

283174-5 

50.57- 7-4 

0.54 15.4 

3 - 37 - i- 6 

3 1 - 7 

98.7 

* 30.4 

Allington Knoll 

- 

2199^6.3 

144032.3 

56.46.43.5 

SE 

262895.3 

51. 4 4 6 - 1 

0.57. 9.4 

3 48-37.6 

3 2 3*5 

5-5 

329 

High Nook near Dymchurch 

- 

228246.4 

165672.9 

54 - J’ 33-4 

SE 

282055.3 

51. 1. 11 7 

0.59.14.6 

3.56.58.4 

22.1 

5-5 

27.6 


Padlefworth - 


261707.6 

130836.4 

63.26 ib. 8 

Sk 

292590.2 

51.6 50.36 

1. 8. 9- 

4 32 36. 

621.3 

20.7 

642 


jbvvingfield - - - 

- 

273722.7 

118730.9 

66.33 2 

E 

298364.1 

51. 8.47.8 

1.11. 14.6 

4.44.58.4 

47 3 - 1 

• 56-9 

53 ° 


Folkftone Turnpike 

- 

274967.3 

137214.2 

63.28,47.6 

SE 

307302.3 

5 '- 5.45-3 

1.11.29.3 

4 - 4 S- 57 - 2 

569 8 

5-5 

575*3 

: 

Dover Caftle, north Turret of the Keep 
ivlontlambert near Boulogne - 

Rlancnez - r •- 

N. D. at Calais - - - 

Point M near Dunkirk, Merid R. Ob. Paris 
Dunkirk - - - 

303766.8 

382889.6 

394891.7 
427456.6 
538048.2 
54,-058.1 

1-4319.1 
273 *S °-3 
- 197 ' 5 > 5 
184263.3 

1549.8-2 

1 5 2 S 49 -i 

67.44 34 
54 27.59.4 
6 4.28-8 
66.40.50.2 
73 56 . 7-2 
74.25. 7.2 

SE 

SE 

SE 

-.E 

SE 

,SE 

328222 

470509.8 

441471.7 
465480.5 

559912.8 
567929.4 

5 1 * 7 - 47-7 
5 °- 43 - 2 3 
SO- 55 - 3 I 3 
50.57.3c.b7 
51. 1.48.3 
s'- 2 9-3 

1. 10. 2.1 

1.38.45. 
1.42 17-9 

1 50.48.8 

2. 9 - 4 2 .5 
| 2.22. 4. 

5.16. 8.4 
6.35. 0. 
6.49. 1 1.6 
7.23 15 8 
q 18.50. 

9 28. 16. 

373-9 

639 G 

444-5 

140.5 

95 - 1 

409 


SECTION. 



the Trigonometrical Operation . 


2 33 


SECTION SEVENTH. 

r 

An Account of the obfervations made during the courfe of the 
trigonometrical operation for', the determination of terrefrial re- 
fraSlion. Plate X, 


Article I. Preamble . 

. . N' ■ ■ ^ 1 - i ✓ 

ASTRONOMICAL refraction, or that which the rays of 
light fuffer in paffing from the heavenly bodies to our earth, 
hath, by the inveitigations of different philofophers, been nearly 
afcertained. From the theory of dioptrics, as well as expe- 
rience, it hath been proved, that the rays, in coming from a 
very rare into a very denfe medium, are gradually bent down- 
wards, out of their reCtilinear direction, into lines more or 
lefs curved in proportion to the angular diftance of the objeCts 
from the zenith, where obliquity ceafing, refraCtion ceafes 
likewife ; lince from that point light takes the Ihorteft route 
through the refraCting medium to the eye of the obferver* 
Hence it follows, that the apparent altitudes of celeftial ob- 
jects are greater than they otherwife would be by the quantity 

of this refraCtion, which is greateft at the horizon, amounting 
there to 33C 

The late Dr* Bradley from his experience has fhewn, that 
in the mean ftate of the barometer taken at 29.6 inches, and 
of Fahrenheit’s thermometer at 50°, the refraCtion at 45® 
of altitude is 57" (according to Dr. Maskelyne only 56 // I). 
Vol.LXXX. Hh In 


2^4 Roy’s Account of 

In other Rates of the atmofphere, it varies with the height of 
the barometer, and inverfely with that of the thermometer 
augmented by the number 350 to the number 400. 

It is therefore obvious, that terreftrial objects as well as 
celeftial, rauft fuffer a refradlion greater or lefs, according as 
they are lefs or more removed from the horizon ; and thatfup- 
pofing celeftial refradlion to be perfedlly aicertained, the mea- 
fure of the lower part of any of its curves, co-inciding with 
a particular objedl on the furface of the earth, fhould give the 
quantity by which the apparent altitude of that objedl would 
exceed its real altitude, or what would be its angle of eleva- 
tion, if no fuch effedl as refradlion did exift in nature. 

The inftrument made ufe of in the triangular operation was 
extremely well calculated, as will be remembered from its 
defcription, for meafuring with much exactnefs fmall angles of 
elevation or depreliion, and confequently was in that rcfpedt 
very fit for the purpcfe, if the multiplicity of other bufinefs 
we had on our hands at the time had permitted refraction to 
become a primary, inftead of being only a fecondary objedl. 
This will readily be conceived by thofe who have any idea of 
the trouble of condudting, efpecially at a late feafon of the 
year, an operation of the nature of that in which we were 
engaged. Along with the lights on the French fide of the 
Channel, we had by day as well as by night our own inland 
obfervations to attend to; the very circulation of orders to the 
men ported at the different Rations from twelve to fifteen or 
twenty miles off, in different diredlions around the horizon, 
when any part of the arrangements failed, fo as to render a 
repetition of lights neceffary, was not a matter of fmall 
detail* 


2 


But 


the 'Trigonometrical Operation. 235 

But befides the important bufmefs of the triangles, which 
engrofled alrnoft our whole attention, it is fufficiently obvious, 
that, in order to have been enabled to make conclufive obferva- 
tions, the relative heights of the ftations fhould in ftri&nefs 
all have been afcertained by levelling : for purpofes of this fort 
geometrical determinations, however good in other reflects 
they may be, Ihould not here be admitted, becaufe they in- 
volve the very point in queftion, that is, the height, which 
fhould be obtained independently of angular meafurement. 
Befides barometers and thermometers at both ftations, two ob- 
fervers and two inftruments of the fame kind would have been 
neceffary, for taking at the fame inftant the reciprocal angle of 
elevation and depreffion 

Although, therefore, in our fituation the circumftances did 
not admit of conclufive obfervations on terreftrial refraction, 
confidered either by the mean or its extremes ; neverthelefs, 
fince in a variety of cafes angles both of elevation and depref- 
fion were reciprocally obtained at the fame ftations, but at dif- 
ferent times, it is hoped, fuch new light will be thrown on the 

% Dr. Maskelyne, in a letter that I lately received from him, remarks, that it 
would be of ufe to have a perfon to note the thermometer at the object as well as at 
the ftation of the obferver, whereby (if niceties of this fort were of confequence) 
the refraction might be more accurately computed by the application of a new cor- 
rection Thus, calling r zr — z= Toth of the arc of diftance ; h — the height of 

IO 

the uniform atmofphere ; t ~ the difference of the thermometers at the two 
ftations ; writhe difference of altitude of the two ftations above a common level : 

the correction would then be — ; and the true or whole refraCtion would 

40 ox 

be zrrrp according as the thermometer flood lower or higher at the upper 

400* & 11 

ftation. 


H h 2 


matter 


2^6 Gen. Roy’s Account of 

matter as may poffiblv hereafter lead to further inveftigatlons 
of this curious, but at prefent vague and indetermined fubjeft : 
for from thefe obfervations it will appear, that terrefirial re- 
fraction, inftead of being -ith of the comprehended arc, accord- 
ing to M. Bouguer, _^th according to Dr. Maskelyne, 
r * th according to M. Lambert, varies from \ to -J-th part 
of that arc; and perhaps, if it had been portable for us to have 
tried it on heights- confiderably more elevated, we fhould have 
found it almoft wholly to vanifh. 

Art. II. Relative heights . 

Before we proceed to give any account of the obferved angles 
* of elevation or depreffioti, at the Rations reciprocally, for try- 
ing the quantity of terreftrial refraction, it will be proper to 
call to remembrance, that, in the meafurement of the bafe on 
Hounflow Heath, the mouth of the pipe at Hampton Poor- 
houfe was (hewn to be elevated about 60 feet above low-water 
fpring tides at the fea, as far as could then be determined by 
referring it to the furface of high water at Ifleworth ; and that 
the extremity of the bafe near King’s Arbour was found by 
levelling to be higher than the former end by 31 feet 3 inches. 

The mouth of the pipe at the fouth-eaft end of the bafe of 
verification at High Nook near Dymchurch, in Romney Marflh, 
Lieut. Fiddes found by levelling to be above low-water mark 
at fpring tides 22.1 feet. 

The top of the parapet of the north turret of the Keep of 
Dover Caftle was found by Lieut. Hay, of the Royal Engi- 
neers (by levelling from the top of the cliff at Queen Eliza- 
beth’s gun downwards, and adding to that the height of the 

7 



the Trigonometrical Operation . 237 

ground and Caftle above the faid gun) to be 465.8 * feet above 
low water at fpring tides. Having alfo meafured a bafe for the 
purpofe, he determined the height of the cliff geometrically, 
which agreed within lefs than a foot of the refult by levelling. 
In juftice to this very meritorious Officer it is incumbent on me 
to lay, that not only on this occafion, but on every other during 
the progrefs of our operations near Pover, his affiftance was 
moft eflentially ufeful. 

The height of the ball of St. Paul’s above the Thames at 
Paul’s Wharf, and the height of Shooter’s Hill Inn above the 
Gun Wharf in Woolwich Warren, were feverally determined 
in 1773, at which time the experiments were carrying on for 
the purpofe of finding a theory for the meafurement of alti- 
tudes by the barometer. 

The height of Severndroog Caftle, lately built on Shooter’s 
Hill, has fince been deduced from that of the Inn. 

Lafrly, the altitudes of all the intermediate ftations, as 
exprefled in the three colums towards the right hand of the 
general table of refults, placed at the end of the preceding 
feftion, have been eftablifhed by the reciprocal angles of eleva- 
tion or depreffion, gradually carried on from ftation to ftation, 
throughout the whole feries of triangles, whereby the two 
extremities are connefted together ; and no greater uncertainty 
has been found at Hampton Poor-houfe than a few feet, occa- 
fioned no doubt by the uncertainty of terreftrial refradlion : for it 
is to be remarked, that, to the weftward of Greenwich, no double 
but only fingle obfervations were obtained; wherefore, the 

* Sir Thomas Hyde Page, when engineer at Dover, at my requeft, had been 
fo obliging as to order his workmen (he himfelf being ill at the time) to deter- 
mine the height of the turret of the Keep, which, by a miftake of about nine 
£eet in the height of the cliff, they made 475 a ^ ove low-water mark. 


rela- 


238 Gen. Roy’s Account of 

relative heights of thefe Rations have been determined by taking 
_ *__th of the arc of diRance for the effect of terreRrial 

I o 

refradlion. 


Art. III. General Theorem. 

Let C (Plate X. fig. 1 1 ) be the center of the earth confi- 
dered as a fphere ; Si the fur face ; H b two places at the fame 
height above the furface ; HO the horizontal line, or apparent 
level at the place H ; and ho the horizontal line, or apparent 
level at the place h ; alfo, let Cm bifedt the angle at C. 

Then, becaufe the angles m HC and mn H are right 
ones, the angle mHn, or mhn, is equal to the angle m CH 
or mCh ; that is to fay, if two places H, h, are of equal 
heights, the one as fieen from the other is depreffed below the 
horizontal line of the place of obfervation, by an angle equal 
to half of the arc of the great circle contained between them, 
or half the angle at C. Hence it follows, that any diftant 
obje£l is higher or lower than the place of obfervation, accord- 
ing as the depreffion is lefs or greater than half the contained 
arc, fuppofing no fuch effect as refraftion to exift in nature. 

Art. IV. Determination of the refraShon between Dover Cajlle 

and Folkfone Turnpike . 

Let D (fig. 12.) be the place of the axis of the telefcope on 
the north turret of the Keep in Boyer Caflle ; T the ground at 
the Ration near Folkftone Turnpike ; DO the horizontal line; 
and SL=CD» 

The diRance of the Rations is 31554.6 feet, which, taking 
the obliquity of the direction into confideration, gives 61 188 
fathoms =i°; and confequently f 9". 4 for the length of the 

contained 


the Trigonometrical Operation. 2 39 

contained arc of diftance nearly, one-half of which, or %' 34".?, 
is equal to the angle ODL. 

At the flat ion D, the ground at T was, by obfervation, 
elevated 8" 37" equal to the angle TDO, to which adding 
ODL=2 7 34 /7 .7, we have for the angle TDL n / n / 7 .j . 

Now, if the diftance of the ftations be taken as radius, the 
lines TO, TL, &c. will be nearly as the tangents of their op* 
pofite angles; therefore the angle TDL, with the diftance 
3 r 554*6 give TL= 102.7 fe el b or what the ground at the fta- 
tion T would have been higher than the axis of the telefcope 
at D, if there had been no refra&ion. 

But the axis of the telefcope, when at the ftation T, was 
5.5 feet above the ground ; therefore 102.74-5.5= 108.2 feet 
would be the height of the axis at T above the axis at D. 

Now, let T (fig. 12..) be the place of the axis of the tele- 
fcope, when the inftrument flood at Folkftone Turnpike ; D 
the top of the parapet of the north turret in the Keep of Do- 
ver Caftle ; TO the ho rizontal line ; and CL=ST. 

At the ftation T, the parapet of the turret was by obferva- 
tion deprefled 14' 17T 5 = OTD, from which fubtrading half 
the arc of diftance 34L7, there remains for the angle LTD 
1 1' 42 // .S. This laft angle, with the former known diftance, 
give LD = 107.5 feet, or what the parapet was lower than the 
axis at T, if there had been no refraction. 

But the axis of the telefcope when at D was 3.2 feet above 
the parapet; hence 107.5-3.2=: 104.3 * s w ^ at the axis at D 
would be lower than the axis at T. 

In this cafe it is evident, that half the fum of 108.2 and 
104.3, or 106.25 feet, is the difference of the relative heights 
of the axis at the two ftations by a mean refraflion ; and that 
this mean refraClion is fubtended by half the difference, or 

ic8.2 


240 Gen. Roy’s Account of 

108.2- IQ 4j ,. T g c feet. Hence, as the diRance = 31 554.6 : 
‘ 2 . 

rad :: 1.95 : tang. i2".8the mean ref ration. 

For ftippofe t (fig. 12.) to be the true place of the ground, 
then the elevation TDO - the refra&ion = TD/, or 8' 37"- 
12". 8 '=%' 24 // .2 = the angle /DO; therefore /DO + ODL = 
ic/ 58A9 = /DL ; whence /L= 100.8 feet, to which adding 
5.5 feet, the height of the axis above the ground, we have 106.3 
feet, the height of the axis at T above the axis at D as before. 

Alfo, if d (fig. 13.) be the true place of the parapet, we (hall 
have the depreffion + the refraction, or OTD + D7V= QTV= 14' 
30 A3, and OTV-.OTL, or 14' 3o // . 3 -2 / 55", 6 

= the angle LTV. Hence, Ld— 109.5 feet is what the para- 
pet of the turret would be lower than the axis at T, from 
which taking 3.2 feet, the height of the axis above the para- 
pet, there remains, as before, 106.3 feet, for the difference of 


the heights of the two Rations. 

The axis of the telefcope in Dover Caftle being Feet, 

above low-water fpring tides . . 469. 

To this add the height of the axis at the 
turnpike above that at Dover . . *06.3 

We then have, for the height of the axis at the 
turnpike above low water, nearly . . 575*3 


And 5' 9 /7 .4 the contained arc of a great circle or arc of 
diftance being divided by i2 /7 .8, the mean refradtion at the two 
Rations, we have in this inflance about part for the quan • 
tity of terrejirial refraction* 


X 


Art. 


the Trigonometrical Operation. 


241 


- ^ 

Art. V. Refraction on the dijlance between Dover Cafle and 

Calais. 

Let D (fig. 14.) be the place of the axis of the telefcope, 
on the north turret of the Keep in Dover Caftle, as before ; 
G the top of the great baluftrade of the fteeple of Notre Dame 
Church at Calais ; DO the horizontal line ; and CL= SD. 

The diftance of I 3 over from ^Calais by the triangles is 
1 3745 ° ^ eet > which, allowing 61169' fathoms for a degree, 
gives 22 28 .2 for the length of the contained arc nearly . 
half of which if 14". 1 is equal to the angle QDL. 

The height of U above low water at jpring tides, 
as before, is ... . 469 feet. 

The height of G is . . . 140.5 


328.5 = CL. 

* ' 

8 i3=LDG, 
~ir 14. 1 


Therefore the difference is 

Then, as 137450 : rad :: 328.5 : tang. 

To which adding the angle ODL 

We have . • • • 19 27.1 for the 

angle ODG, or what G would be depreffed below the place of 
obfervation, if there was no fuch effeft as refra&ion. But the 
depreffion by obfervation was found to be 1 7 / 5p ;/ ; wherefore 
the difference is 28 // . 1, by which, dividing the length of 
the arc of diffance 22 7 . 28 v .2, we have in this infance 1 ^.3, or 
between ~ T th and ^ w th 'part , for the quantity of terrefrial 
refraction. 

Art. VI. Refraction on the di/lance between Aliington Knoll and 

Tenterden . 

Let K (fig. 15.) be the place of the axis of the telefcope at 
Aliington Knoll; T the top of the flag-ftaff on Tenterden 
Von. LXXX. I i Steeple ; 


2 ^ 2 Gen. Roy’s Account of 

Steeple; SC the earth’s furface ; KO the horizontal line at 

right angles to KC ; and SL = CK. 

The diftance between Allington Knoll and Tenterden has by 
the triangles been found to be 61775.3 feet, which, allowing 
61234 fathoms = i° gives 10' 5". 3 for the length of the con- 
tained arc CS nearly. Half of this arc = f 2 ". 6 is the angle 
OKL, from which fubtra&ing the obferved angle of depreflion 
of T as feen from K = OKT = f 51", there remains the angle 
TKL=x 7 ii". 6, and confequently this angle will be fub- 
tended by 21.4 feet=LT, or what the top of the flag-ftaff at 
Tenterden would have been higher than the axis of the tele- 
fcope at the Knoll, if there had been no refraflion. 

But the top of the flag-ftaff on Tenterden fteeple was 3.1 
feet higher than the axis of the telefcope when the inftrument 
flood at that ftation ; therefore, 21.4 -3.1 = 1B.3 is what the 
axis at Tenterden would have been higher than the axis at the 
Knoll, if there had been no reflation. 

Again, let T (fig. 16.) be the place or the axis of the tele- 
fcope on Tenterden Steeple ; K the ground at the ftation on 
Allington Knoll ; TO the horizontal line ; and CL = ST . 

At the ftation T, the depreflion of the ground at K, or the 
angle OTK, was obferved 3' 55 / \ which being fubtra&ed from 
^ 2 // .6 = OTL = half the arc of diftance, there remains 
i v 27^.6 = the angle KTL. This laft angle, with the diftance 
between the ftation s, 61775.3 feet, give KL=26.3 feet, for 
what the ground at K would have been higher than the axis at 
Tenterden, if there had been no refra&ion. 

But the axis of the telefcope, when at the ftation K, 
was 5.5 feet above the ground; therefore, 26.3 + 5.5 = 31-8 is 
what the axis at the Knoll would be higher than the axis at 
Tenterden* 


1 


Hence 


the Trigonometrical Operation. , . 3 ^_ 

Hence It follows, that fuppofing the refradion to have been 
the fame at, each of the ftations when the obfervations were 

made, half the difference of thefe heights, or - 3 i,8 ~ i8 ' 3 - (, - 

feet, would be the difference between the relative heights of 
the axis at the two ftations ; and that the quantity of refrac- 
tion would be fubtended by half the fum, or 31,8+ i8 ~ 3 - 2 ^ Q 

feet ; therefore, to find the mean refradion, as the diftance of 
the ftations : rad. :: 25.05 feet : tang. 1^23"! the mean 
refra&ion. 

For fuppofing t (fig. 1.5.) to be the true place of the top of 
the flag-ftaff, we fhall then have the angle OKT the depreffion 
+ the angle TK/ the refradion, or $1" + T 23"! = 5' l4 " | 
= the angle OK/. Hence the angle OKT - the angle OKL = 

5 *4 i~S 2 •6 = o / 1 1 !/ .<) — the angle LK/. Now, this laft 
angle, with the diftance of the ftations 61775.3, give L/ = 3.6 
feet, or what the top of the flag-ftaff at Tenterden would be lower 
than the axis at the Knoll; and this being added to 3. 1 feet 
(what the axis at Tenterden was lower than the top of the 
flag-ftaff), we get, as before, 6.7 feet for the height of the 
axis at the Knoll above the axis at Tenterden. 

In like manner, fuppofing k (fig. 16 ) to be the place of the 
ground at the Knoll, we have the fum of the depreflion and 
refradion, or OTK -fKT/r—o' 21" + 1' 22"*=*' rS^x* 
0 «; and OtL-OTfej' j8"|=o' 4 "fi = the 

angle £TL» Hence, kt= 1.2 feet is the height of the ground 

at the Knoll above the axis at Tenterden, which being added 

to 5.5 feet the height of the axis at the Knoll above the 

ground, we have as before 6.7 feet for the difference of the 
heights. 


I i 2 


The 


244 


Gen . Roy’s Account of 


Feet, 


The height of the axis of the telefcope at Allington 
Knoll above low-water mark at fpring tides, as deter- 
mined by the obfervations there, and at the ftation of 

High Nook, is • • • • 3 2 9 

The axis on Tenterden Steeple has been (hewn to be 

lower than the Knoll . ®*7 

Therefore, the axis on Tenterden Steeple is higher 
than low water . 3 22 -3 

The arc of diftance of the two ftations «= io' 3". 3 being 
divided by i/ if'z the mean refraCtion, we have in this cafe 
or between \th and ^tb part for terrefrial refraSlion. 

The example in Art. IV. and this laft are given at large, 
becaufe, if the points where the axis of the telelcope was at the 
refpe&ive ftations had been obferved, in the firft, one would 
have been a depreflion, and the other an elevation ; but in this 
both would have been deprefled by obfervation. 

Art. VII. General Remarks. 

The three preceding examples being fufficient to (hew the 
mode that has been invariably adhered to in computing tne 
effect of terreftrial refraction, we have, in the following table, 
collected the whole of the refults together, beginning with 
thofe diftances where it has been found the greateft, and ending 
with thefe where it has been found the leaft. 

The titles at the tops of the columns refpeftively fully ex- 
plain the nature of the table, which contains more double ob- 
fervations, made on a greater variety of very accurate diftances, 
and with a better inftrument for determining fmall angles of 

elevation and depreflion, than perhaps were ever obtained be- 
fore. 


the Trigonometrical Operation . 


245 


fore, Thefe refults are not however offered as being free from 
error; on the contrary, if the circumftances had permitted this 
to become a principal objedt in our operation, the fucceffive 
repetition of the obfervations for many times would, no doubt, 
have furniftied ftill more fatisfadtory conclufions. It is hoped, 
neverthelefs, that thefe, fuch as they are, may have their ufe, 
were it only by fhewing the variablenefs of terreftrial refrac- 
tion, to induce to the making of others, which, as has been 
already obferved, would ultimately lead to a much more mi- 
nute inveftigation of this curious and interefting fubjedt. 

The heights of the barometer and thermometer are inferted 
on the days on which the obfervations were made, merely to 
fhew what was nearly the ftate of the atmofphere at the refpec- 
tive times. But we have not attempted to apply any corredlion 
on that account, becaufe it could not be done in a fatisfa&ory 
manner, and coniequently could not be ufeful, unlefs the cir- 
cumftances had permitted reciprocal obfervations to have been 
made at correfponding times with double fets of inftruments, 
which in our fituation was impoffible, 

By attending to the refults in the tahle, it will in general be 
feen, that terreftrial as well as celeftial refraction certainly di- 
ffiinifhes as the heights of the ftations above the fea increafe; 
and that, at particular times at leaft, it is much greater than 
has hitherto been fuppofed, even to between § and §■ part of 
the arc of diftance, inftead of being only gth or part. 

Befides the inftance of this extraordinary effedt inferted in the 
table, between Allington Knoll and Ruckinge, where the dif- 
tance of the ftations is but fmall, and one of them little 
high er than the fea, we could have given another on a diftance 
as well as on heights ftill more confiderable, namely, Shooter’s 
Hill and the ball of St. Paul’s Church : for, fuppofing the 
2 ' firft 


g Gen. Roy’s Account of 

firft to be 482, and the laft 403 feet, above low water at the 
fea, the refraction on the morning of the 1 ft of September, 
i 7 8 7 , as obferved at Shooter’s Hill, was which is be- 

tween f d and |th part of the contained arc. 

If the circumftances had permitted the reirachon on the 
diftance between Dover and Calais to have been repeatedly 
tried, at the bottom of the cliff, at the top of the cliff, and 
again at the top of the caftle, we (hould probably have found 
the refraftion at the three ftations confiderably different, with 
tire fame length of arc, or one only varying infenfibly. 

But, in order to be enabled to make conclufive obfervations 
of this fort, the. operation fhould become a diftinfft one, or at 
moft only comprehend fuch others as aie conneaed with the 
modifications of the atmofphere. For purpofes of this kind 
very fine levels would be requifite ; and fome of the higheft 
mountains of Scotland, fituated near the fea, fuch as Ben 
Nevis and Cruachan Ben , where the relative heights of the 
ftations might be accurately afcertained by levelling, would 
feem to be eligible fituations. 



Tablb 


Table containing the Results of the Observations for the Effect of Terrestrial Refraction. 


Dates of the 
Obfervations. 

Places. 

Bar. 

Therm 




In. 

Q 

1787, Oft. 21. 

Allington Knoll 

- 

29.61 

56 

23- 

Ruckinge 

- 

29.82 

5ii 

19. 

Dymchurch Inn 

- 

29.9 

552 

21. 

Allington Knoll 

- 

29.61 

56 

19. 

Dymchurch Inn 

- 

2 9 . 9 

552 

21. 

Allington Knoll 

- 

29.61 

5 6 

26 . 

Tenterden Inn 

- 

29-54 

56* 

7- 

Padlefworth 

- 

29.6 

70 

1788, Aug. 18. 

Frant Inn 

- 

29.36 

58 

2 3- 

Botley Hill 

- 

28.89 

62F 

1787, Sept. 28. 

Dover CJaltle 

- 

29.62 

58f 

Oft. 7. 

Padlelvvorth 


29 6 

70 

i3- 

fanlight Down 

- 

28.81 

552 

26. 

Tenterden Inn 

- 

29 54 

5 b f 

26. 

Tenterden Inn 

- 

2 9-54 

561 

1788, Aug. 11. 

Goudhurft Churchyard 

29.74 

sU 

18. 

Frant Inn 

- 

29.36 

58 

1787, Oft. 13. 

Fairlight Down 

- 

28.81 

55f 

1788, Aug. 11. 

Goudhurft Churchyard 

29.74 

sH 

1787, Oft. 26. 

Tenterden inn 

- 

29-54 

sH 

21. 

Allington Knoll 

- 

29.61 

5 6 

Sept. 28. 

Dover Caftle 

- 

29.62 

58| 

1788, Sept. 2. 

Folkltone 'Turnpike 

29-55 

64 


Stations. 

Height of the 
Telefcopeabove 
the Sea in Feet 

Diftance 
of the Station 
in Fathoms. 

Contain- 
ed Arc 
nearly. 

Mean 

Refraftion. 

Proportion- 
able Part. 

j Allington Knoll and Ruckinge — j 

A. 

R. 

329 - 1 
37-4 1 

2675-4 

y 

2 

// 

38 

I 

// 

8 

i and -j 

High Nook and Lydd — j 

H. 

L. 

27.6 I 
1 3°-4 J 

5227.1 

5 

8 

O 

55 

I and 4 

j Allington Knoll and High Nook — j 

A. 

H. 

329 - 1 
27.6 ] 

3864.1 

3 

48 

0 

38 


| Allington Knoll and Tenterden — — j 

A. 

T. 

329 - 1 

322.3 I 

10296. 

IO 

5 

I 

2 3 § 

7 and -J 

Padlefworth and Lydd — j 

P. 

L. 

624. | 

! 3°-4 J 

I 3 2 55-5 

13 

2 

1 

3 i 

i 

| Frant and Botley Hill — . . j 

F. 

B. 

& 59 - 1 
880. j 

15060.7 

14 

48 

2 

I 

X 

8 

j- Dover Caftle and Padlefworth — j 

D. 

P. 

ft ) 

7 ° 93-5 

6 

,57 

O 

42 

X 

TS 

| Fairlight Down and Tenterden — j 

F. 

T. 

599 - \ 
322.3 J 

11939.1 

I I 

46 

I 

12 

X 

T<y 

Tenterden and Lydd — — j 

T. 

L. 

322-3 1 
1 3°-4 J 

11027.8 

IP 

5 ° 

O 

55 ! 

j 1 , and T \ 

| Goudhurft and Frant — — { 

G. 

F. 

497 - 1 
& 59 - J 

7398-3 

7 


O 

382 

TT 2nC ^ A 

Fairlight Down and Lydd — — j 

F. 

L. 

599 - 1 

• 3°-4 J 

12948-3 

II 

43 

O 

55 

X 

TT 

] Goudhurft and Tenterden — — j 

G. 

T. 

497 - ] 
322-3 J 

9062.4 

8 

53 

O 

35 

TT 

Allington Knoll and Lydd — — j 

A. 

L. 

329 - 1 
1304 J 

7975 - 

7 

5 i 

O 

21 

1 

TT 

| Dover Caftle and Folkftone Turnpike j 

D. 

F. 

469. j 
575-3 J 

5259.1 

5 

9.4 

O 

12.8 

r 

IT 


Results of 

Single Observatj 

ONS 

lependin 

g on the Heights of Dover Caftle anc 
Coaft of France. 

Fol 

kftone 1 

^urnpike, cc 

imbined 

with tho 

e on the 

1788, Sept. 2. 

1787, Sept. 28. 

1788, Sept. 2. 

— — — 

29.55 

29.62 

29-55 

64 

58! 

64 

] Folkftone Turnpike and N. D. Church at Ca- j 
J lais ( 

Dover Caftle and N. D. Church at Calais j 

1 Folkftone Turnpike and Station at Montlam- f 
J bert — — — 1 

F. 

C. 

D. 
C. 
F. 
M 

575-3 1 
140.5 J 
a6 9 . j 
140.5 J 
575-3 1 
639-5 J 

26697. 

22908. 

28967. 

26 4 

22 28.2 
28 29 

3 54-8 

0 15.4 

1 45- 

i and 4 
* tV and -j% 

T 7 


SECTION 



. - - ri 


the 'Trigonometrical Operation. 


247 


SECTION EIGHTH. 

1 

Secondary triangles , fubdivided into two fets, for the improve- 
ment of the maps of the country , and the plan of the City of 
London and its Environs • Plate XL 


IN the feries of great triangles, whereby the diflance be- 
tween the meridians of the Royal Obfervatories of Greenwich 
and Pans has been determined, the fame excellent inRrument 
havin been placed at every Ration on our fide of the Channel, 
and all the angles obferved with the utmoR care, it hath con- 
fequently followed, that the bafe on Hounflow Heath, and 
that in Romney Marfh, reciprocally meafure each other within 
a few inches of the truth, which is an inftance of fuch exa£l- 
nefs as probably never occurred in any former operation of this 
fort. The extreme fmallnefs of the error on the fum of the 
three angles of each triangle lufficiently proves that the ge- 
neral refult would not have differed greatly, if only two of the 
angles had actually been obferved. But in an operation of fo 
much importance, this could not have been depended upon ; 
nothing was to be left doubtful ; and therefore, in the execu- 
tion of the various parts, the moR minute attention was paid 
to every circumftance whereby the accuracy might be afFefted, 
and particularly to the placing of the lights and inRrument 
reciprocally over the fame point marking the Ration, that no 
poflible error might arife from parallax or excentricity. 


From 


24 g Gen . Roy’s Account of 

From this mode of conducing the operation, it will 
readily be feen, that, if time had permitted, the iituation of a 
multitude of other points in the country might have been very 
accurately determined, hefides thole actually marking the 
points of the triangles, whereby the ordinary maps would have 
been greatly improved bv fuch as chofe at any time hereatter to 
make ufe of thefe as fo many given diftances. hut the circum- 
ftances not having permitted us to multiply thole points to the 
extent that might have been wifhed, and that would have been 
e a lily pradicable, if the operation had commenced at an earlier 
feafon of the year ; we have therefore been obliged to limit the 
number to a few of the mod confpicuous and bed defined objeds. 

Thefe fecondary triangles are fubdivided into two lets. The 
firft fet conlifts of thirty-five, whereby the relative diftances offo 
many points have been determined from certain ftations of the 
principal feries, beginning with thofe objeds that have been in- 
terfeded from the moft wefterly ftations, and lo on, proceeding 
gradually with the others towards the eaft. Two angles only 
of each of thofe triangles being obferved, the third is that at 
the interfeded objed, or the fupplement to i8o°. Although 
the diftances thus obtained cannot be quite lo accurate as the 
fide s of the principal feries ; yet there is no reafon to appre- 
hend, that they will be found to differ widely from the truth, 
when the}/ come to be proved in the courfe of any fubfequent 
* operation, by which alone the}/ can be put to the teft. 


f . i i 


Com- 


the ’Trigonometrical Operation. 


249 


N° 

Computation of th 

Triangles. 

e firft fet of 

Angles. 

‘ , \ 

fecondary triangles. 

Diilances of the flations from the 
interfered object in feet. 

r 

1. - 

iRing’s Arbour 
St. Ann’s Hill 
Stanwell Church 

0 / // 

8 5 2 57 
4 4 44 
167 2 19 

| from Stanwell „ j 

- 

10927 

23720 

a 

[Ring’s Arbour 
Hanger-hill Tower 
Harrow on the Hill 

- ) s 

28 35 34 

89 23 52 
62 0 '34 

j from Harrow on the f 
j Hill | 

42944 

2 ° 553-3 

3 * * 

V, 

[King’s Arbour 
Hanger-hill Tower 
Ban/lead Church 

70 i 47 
82 19 25.1 
27 38 47.9 

| from Banhead Church | 

80994 

76807.5 

r 

4. < 

V 

jHampton Poor-houfe 
iKing’s Arbour 
j Kew Pagoda 
1 

88 58 23 
40 14 25 
50 47 12 

j from Kew Pagoda . j 

22849 • 

35364-5 

s; { 

Harrow on the Hill 
St. Paul’s Church 
Spring Grove Houfe, Sir Jo. 
Banks 

69.43 8 

35 5 8 9 

74.18 43 

1 from Spring Grove f 
J Houfe j 

3585! 

57253-9 


Hanger hill Tower , 

Spring Grove Hc?ufe % 

'Richmond Royal Ohfervatcry 

l 9 33 4-3 
82 46 15.9 

] 

77 40 39.8 

f frorn^ Richmond Royal J 
1 Gbfervatory 
Hangey Hill from Spring 
Grove . 

20164.4 

6802.1 

: 9 8 57 8 


f The Royal Gbfervatory in Richmond lower Park could not be .'Teen from any 
of the ftatipns of the great feries of triangles, except Hanger-hill Tower, from 
whence the bearing of it was taken. In order to interfedt this bearing, the afif- 
tance of certain operations made with the agronomical quadrant in 1783 at 
Spring Grove Houfe has been called in, by the help of which the iituations of the 
Gbfervatory and of Spring Grove Houfe have been determined. In like manner, 
the bearings of Batterfea and Stretham, taken from Hundred Acres, have been 
interfedled with the quadrant from St. Paul’s and Fulham, The flations where the 
quadrant was ufed are diftinguifhed with aherilks, 

K k * N oi - 


Vol, LXXX. 


Gen. Roy’s Account of 


N° 

Triangles. 

Angles. 

Diftances of the ftations from the 
interfered object in feet. 

’■ 1 

Hundred Acres . • 

St. Paul’s * 

Batter fea Church • • 

0 / // 

14 13 27 

34 3 49 * 2 
131 42 43.8 

J from Batterfea Church | 

50664.5 

22226 

8 { 

Hundred Acres 
Fulham Church -Jf • 

Stretham Church 

27 5 1 55 * 6 
46 12 54.4 
105 55 10 

| from Stretham Church j 

35957-3 

23 2 79'3 

r 

9 . < 

V 

Hundred Acres 
Severndroog Caftle 
Claph^m Common, Mr. Ca- 
vendish • • 

3 6 59 35 - 8 
33 28 20.5 

109 32 3.7 

j from Clapham Common j 

43351*7 

47296.4 

IO. - 

V. 

Norwood • • 

Severndroog Caftle • 

Argyll Street Oh. Maj . Gen. Roy 

76 19 14.5 

5 2 4 r 37 
50 59 8 *5 

1 from Argyll Street Ob- f 
j fervatory [ 

40083.2 

39963 

II. - 

Norwood • • 

Severndroog Caftle • 

St, Paul's Church 

N. B. By combining the refu 
which gives for the diftance of 

62 30 23.5 

57 8 8 *5 
60 21 28 
Its of thefe two h 
Argyll Street fre 

| from St. Paid’s Church j 

ift triangles a third is formed, 
>m St. Paul’s 

37840.9 

39963 

9632 

r 

12. - 
! > 

Norwood * • 

Severndroog Caftle 
Bromley College 

36 36 32 
32 52 48 
no 30 40 

| from Bromley College j 

22695.4 

24930.6 

C 

13- * 

V. 

Norwood • » 

Severndroog Caftle • 

Cblfiehurft Church 

3 1 53 3 
67 48 12.5 

80 18 44.5 

| from Chiflehurft Church j 

35777*9 

20981.1 

14- 1 

Greenwich Royal Obfervatory 

Severndroog Caftle 

IVeJl Pediment of Wanjlead Ho. 

9 2 3 8 * 3-5 
64 46 33-5 

22 35 13 

| from Wanftead Houfe j 

344 1 3 - 6 
37999*7 

IS | 

Greenwich Royal Obfervatory 
Severndroog Caftle « 

^ Loam fit Hill 

131 45 43 
14 7 0 

34 7 i 7 

J from Loampit Hill j 

6352.6 

19428.4 

,6.| 

* Greenwich Royal Obfervatory 
Severndroog Caftle 
1 Beckenham Church 

8 5 49 9 
63 29 48 

3 ° 4 i 3 

| fromBeckenhamChurch j 

25622 

28 555 


N° 


the Trigonometrical Operation . 


2 5 l 


N° 

Triangles. 

Angles. 

Diftances of the ftations from the 
interfe&ed obje£t in feet. 


' Greenwich Royal Obfervatory 
Severndroog Caftfe 
„ Eltham Church 

Of// 

22 41 33 
87 l8 

6 9 59 55-5 

| from Eltham Church j 

* 553 * 

599 8 -3 

18. | 

Severndroog Caflle 
Botley Hill 

Knockholt Beeches * 

21 56 44 
54 48 27 
103 14 49 

| from Knockholt Beeches j 

5 8 933 
26951 • 

i 9 . 1 

Severndroog Caftle 
Botley Hill 
Leeth Hill Tower 

2 1 AO 20.4 

124 53 *4 
23 26 16.6 

| from Leeth Hill Tower j 

i 

I44761 

92668 

20. i" 

1 

Botley Hill 
Frant Church 
Firedean Tower 

39 17 6.5 

26 58 39 
‘13 44 4-5 

| from Firedean Tower j 

44780.4 

62507 

21. i 

Botley Hill 
Frant Church 
Crowborough Beacon 

19 51 19.5 

77 3 2 33 
82 36 7.5 

1 from Crow bo rough Bea- f 
J con { 

88977 

3 ° 949-7 

22. | 

Botley Hill 
WrotHam Hill 
Sevcnoaks Windmill 

24 22 7 
28 57 42 
126 4O It 

1 from Sevenoaks Wind- f 
/ mill ( 

4403 2 -4 
375*9 8 

2 3 I 

Frant Church * 

Goudhurft Church 
Wadhurft Church 

46 5 9 
26 21 46.5 

»07 33 4*5 

| from Wadhurft Church | 

2O674 

33538-7 

24 . | 

N 

Goudhurft Church 
Fairlight Down 
Brightling Windmill 

42 6 2« 

3 8 5 33 
99 48 2 

1 from Brightling Wind- f 
J mill j 

c86i6.2 

63707.4 

* 5 * - 

V 

Fairlight Down 
Lydd Church 
Rye Church 

22 40 17 
21 23 25 
*35 56 18 

| from Rye Church j 

37598 

39734 

26. 1 

Fairlight Down > 

Dover Caftle, north turret 
Dengcnefs Light-houfe 

*9 34 3 ° 
13 <54 24.6 

r 4 & 3 * 5-4 

\.from Dengenefs Light- J 
J houfe { 

81082.7 
I IgO^O 

. 7 . 1 

Fairlight Down « 

Goudhurft Church 
Ore * Church 

4 12 42 
60 29 28 
”5 *7 50 

[ from Ore Church j 

7605.3 

90123.2 


K k 2 N° 


Gen. Roy's Account of 




N° 

Triangles. 

Angles. 

x— ’ 

Diftances of the ftations from the 
interfered objeH in feet. 

r 

28. < 

V 

Fairlight Down • 

Lydd Church 

Fair light Church « 

0 / // 

23 3 2 23 
3 5 ° 43 
3 S 4 3 6 5 + 

j from Fairlight Church j 

5384 

66787 7 

29. | 

Tenterden Church , 

Allington Knoll 
for cl Church 

3 ° 42 37 
46 45 7 
102 32 l6 

| from Alhford Church j 

^6096 

3 2 3 x 9 * 2 

3 °.. - 

V. 

[Lydd Church . • 

jHigh Nook near Dymchurch 
RucCnge Church 

43 34 5°-5 
87 40 22 

48 44 47 5 

| from Ruckinge Church j 

41682.2 

.8758,4 

r 

1 

High Nook > . 

Ruckinge • 

\New Romney Church 

83 44 33-5 
32 ‘7 35-5 
63 57 5 1 

| from New Romney Ch. j 

16965.4 

31566.3 

32. - 
33 - ■ 

V 

High Nook 
Allington Knoll 
Lymne Cajtle 

42 44 44-5 
70 21 48 

6° 53 27.5 

| from Lymne Caftle | 

2374K6 

17109.6 

Lydd Church 
jFolkftone. Turnpike 
1 FUkftone Church 

i J . . 

2 10 292 
27 26 22 

150 23 8,8 

| from Folkilone Church j 

78946.9 

6501.3 

/* 

34 - - 

V 

iFolkftone Turnpike 
rPadlefworth 

Beachborough Summer Houfe 

24 35 59 
123 46 35.2 

3 1 37 25 8 

] from Beachborough J 
j Summer Houfe 

23325-2 

1 1681.6 

tss- | 

Padlefworth 
Dover Caftle 
IValderJhare Monument 

32 36 O 

62 24 5 
84 59 55 

f from- Walderfhare Mo- 1 
\ * nument 

37862.5 

2308 1.4 


Second Jet of fecondary triangles . 

In the Paper of 1787., fufficient reafons have been given 
for avoiding St. Paul’s as a Ration in the feries of great tri- 
angles. Indeed, if no other objection had exifted, the fmoke 
of the capital alone would have been found extremely incon- 
venient. This was experienced at Shooter’s Hill, where we 


were 


the ‘Trigonometrical Operation. 253 

were detained a whole week, before the white lights, notwith- 
standing their extraordinary brilliancy, could be feen at Han- 
ger-hill Tower, or even at Argyll Street, the north -eat wind, 
which then prevailed, having brought the impenetrable mafs 
of frrioke between the ftation of theindrument and the points 
to be obferved ; and at lad we were obliged to watch all night, 
till tow aids tne morning the fires of L.ondon hemp* extin— 
guifhed, the white lights could then be interfered. 

It is not therefore furprifing, that from the Nations of Nor- 
wood, Greenwich, and Shooter’s Hill, we fhould only be able 
to fix, in a fatisfadory manner, two points in London, namely, 
St. Paul’s and Argyll Street. Bearings, it is true, of others 
were taken ; but that thefe might be interfered by angles not 
too acute, it became neceflary to make ufe of obfervations that 
had been formerly obtained at Argyll Street with my own 
infirument in its vertical pofxtion, and at St. Paul’s with the 
adronomical quadrant. Moreover, by way of finifhing the 
operation, and fumifhing fuch part of the inhabitants of the 
metropolis as may be curious in matters of this fort with a fet 
of didances that cannot fail to be ufeful to them, two new 
dations were chofen for the great infirument to the northward 
of London, one on Hot nj'ey L/j//, and the other on Primroje 
Uni. Thus, from the combined operations at thefe feveral 
places, we have been able to determine the fituation of thirty - 
feven confpicuous points, confiding chiefly of the mod re- 
markable deeples in and near the capital. 

By referring to Plate XI. which is in fad the fkeleton, but on 
a very fmall fcale, for an improved plan of London and its 
environs, the relative fituation of thefe points with regard to 
St. Paul s, and the four neared dations of the great feries, 
will be feen. Some of the principal of thefe fecondary tri- 
3 ... angles 


Situations determined by the great inftrument from 
Hornfey Hill and Primrofe Hill. 


254 Gen. Roy’s Account of 

angles have been reprefented by dotted lines in the plan. To 
have expreffed more of them in that way would only have 
occafioned confufion. Here it is to be remarked, that the 
diftance of Argyll Street from St. Paul’s, 9632 feet, refulting 
from the 10th and 1 ith fecondary triangles of the firft fet, be- 
comes a bafe in the quadrilateral formed by St. Paul's, Argyll 
Street, Hornfey Hill, and Primrofe Hill. Hence, by theobferved 
angles at thefe two laft Rations, and the affumed length of 
one of the unknown (ides, all the angles of the quadrilateral 
are computed, by which means, and the true length of one 
fide given, the true lengths of all the others are readily ob- 
tained. 

N - ' a 


Computation of the lecond fet of fecondary triangles. 


N° 

Triangles. 

Angles. 

Diftances of the ftations from 
the interfered object in feet. 

1. ^ 

Hornfey Hill 
Primrofe Hill 
St. Paul's • 

0 4 // 

46 42 41 
83 21 27.5 

49 55 5 * 5 

1 from St, Paul’s J 
J Church 1 

Hornfey Hill from 
Primrofe Hill 

23297.1 

17072.8 

17949.05 

p 

2e V 

Hornfey Hill 
Primrofe Hill. 

Argyll Street Qbfervatory 

23 8 34 
112 49 s 7 
44 1 2 9 

] Argyll Street Ob- f 
J fervatory \ 

23803.4 

10150.7 

* { 

Hornfey Hill 
Primrofe Hill • 

Hampftead Church 

23 33 59 
78 23 43 
78 2 l8 

] from Hampftead f 
J Church 1 

17972 

7335-5 

4. 

Hornfey Hill 
Primrofe Hill 

Mr. Duveluz’s Cupola , 
Hornfey Lane, Highgate 

29 m 3-5 
16 44 50 

134 4 6.5 

1 from Mr. Duve- f 
J luz’s Cupola 1 

I2l8l. 2\ 

7198.2 

M 

Hornfey Hill 
Primrofe. Hill 
. Iflington Church 

47 3 ° 4 2 
5 ? 42 39 
80 46 39 

| from Illington f 
j Church t 

14272.5 

13409 


N» 


the Trigonometrical Operation . 


2 55 


1 

da 

o 

J-. 

S 

'u 

"C 

a 

rt 

—■ H 

• f-* 

M 

a 

u 

1 < 
4-1 

a 

<u 

s 

3 

u 

ej 

a 

44 

rt 

V 

u 

W> 

o 

-a 

44 

-a 

4—1 

' . —1 
& 

L 

N° 

Triangles. 

Angles. 

Diftances of the Nations from 
the interfered obje£t in feet. 

! 6 - J 

r Horn fey Hill 
Primrofe Hill 

. Highbury Houfe^Mr. Auberi 

0 e // 

55 28 32 
29 28 52 
95 2 36 

1 from Highbury I 
J Houfe j 

8867.7 

14845.4 

7 - * 

' Hornfey Hill 
Primrofe Hill 

St. Lukes Church , OldStreei 

50 52 33 

68 59 37 
60 7 50 

| from St. Luke’s I 
J Church { 

>9323 

,6o 57-5 

8. { 
V. 

Horn fey Hill 
Primrofe Hill 

St. Leonard’s Ch. Shoreditch 

62 9 30 

6 3 3 6 33-5 
54 13 56.5 

1 from St. Leonard’s j 
J Church { 

I9816 

19560.5 

f 

9 * - 

w 

Hornfey Hill . 

Primrofe Hill 

Chrijt Church , Spitalfields 

61 19 7.5 

7 ° 33 39 
48 7 13-5 

1 from Chrifl [ 

J Church, Spit. { 

22733 

21149.3 

r 

10. < 

k 

Hornfev Hill 

Primrofe Hill 

Bow Church , Cheapfide 

49 20 38.5 

81 21 4,5 

49 18 17 

J from Bow Ch. j 

23404.4 

17959.6 

II. - 

Hornfey Hill . 

Primrofe Hill 

St. Bride’s Ch. Fleet Street 

42 33 43 
86 44 24 

5 ° 4 1 53 

1 from St. Bride’s f 
J Church j 

— — 

23158 

15689.1 

r 

12. - 

k 

Hornfey Hill 
Primrofe Hill 

St. George’s Ch. Bloomfbury 

31 16 11 
94 1 * 25 
54 32 24 

' from St. George’s J 
Church { 

21977 

11438 

r 

l 3 - ] 

Hornfey Hill 
Primrofe Hill . 

St. Giles’s Church 

29 32 8.3 

i°° 13 30.5 
50 14 21 

from St. Giles’s J 
Church 1 

22978.4 

11510.4 

14. | 

Hornfey Hill 
Primrofe Hill 
St. Ann’ s, Soho . 

28 2 38 j 
106 40 20 
45 17 2 

| from St. Ann’s J 
J Church { 

24197.1 

11875.4 

One angle taken with 
the great inftrument, 
and the other with that 
in Argyll S reet Obf. 

/ 

I5- 1 

L 

Hornley Hill 

Argyll Street Obfervatory 
High gate Chapel 

59 5 2 55-5 
22 37 47-6 
97 29 16.9 

| from Highgate f 
j Chapel | 

9237.8 

2O766.9 

,6.1: 

u 

Primrofe Hill 

Argyll Street Obfervatory 1 

St. Clement’s Church 

20 43 cO 
23 O 9.4 
36 16 0.6 

1 from St. Clement’s f 
| Church | 

[4200.2 

6073.8 


N° 


25 6 


Gen. Roy’s Account of 


One angle taken with the great 
inftrument, and the other with 
that in Argyll Street Obfervat. 

c — — * > 

N» 

Triangles. 

. 1 1 

Angles. 

Alliances of the flations from 
the interfered object in feet. 

11 ’ { 

Primrofe Hill 
Argyll Street 

St. Mary's Ch. in the Strand 

oil / 

17 5 2 3 1 

[27 21 I. 

34 46 14 

| from St. Mary’s f j 
/ Church 1 

14148.5 

5463-4 

18. 1 

Primrofe Hill 

Argyll Street Obfervatory 

St, Martin's Ch. in the Fields 

7 32 8.5 
152 0 27 

20 27 24.5 

j from St. Martin’s j 
J .Church { 

1 2631.6 
3808.8 

19. 

Primrofe Hill 

Argyll Street Obfervatory 

Pantheon 

3 12 59-5 
102 32 39.4 
74 14 21. 1 

] from the Pan- f 
| theon [ 

10295.5 

591.8 

A fmall Hadley’s | 
fextant ufed in Ar- 1 
gyll Street. 

f 

20. < 

V 

Primrofe Hill 

Argyll Street Obfervatory 

St. George's Ch. Hanover Sq. 

5 35 34 
120 13 56 1 

54 10 30 

| from St George’s f 
j Church [. 

108 16.3 
1 220. 1 

r 

21. - 

Primrofe Hill 

Argyll Street Obfervatory 

South Audley Chapel 

16 7 10 

103 34 - 59 
60 17 51 

1 from South Aud- f 
} ley Chapel 1 

1 1 359*3 

3 2 44-5 

A fmall Hadley’s | 
fextant ufed at St. *, 
Paul’s. 

r 

22. * 

V* 

Horn fey Hill • 

St. Paul’s Church 
Newington Church 

38 14 6 

16 35 7 

123 10 47 

1 from Newington f 

j Church i 

• 

8 1 36.4 
17641 

f 

23- ", 

l 

Horn fey* Hill 
St. Paul’s Church 
St. Matthew's Church , Beth- 
nal Green . . 

20 29 59 
66 7 5 

92 22 56 

1 from St. Mat- J 
| thew’s Church [ 

21321 
8 165.8 

- — T 

The agronomical quadrant j 
ufed at St. Paul’s in 1783. 1 

-A. — — — — k I 

• 

24. * 

' 

Hornfey Hill 
St. Paul's Church 
^ St. George's , Ratcliff' 

18 22 9 
105 32 24 
50 5 27 

1 from St. George’s f 
J Church, Ratcliff \ 

27045.2 

8846.4 

25. - 

'jPrimrole Hill 
St. Paul’s Church 
__ Si, James's Church 

30 44 17 

45 39 3 1 
103 30 12 

1 from St. James’s f 
J Church \ 

12562.7 

8978 

26. - 

l 

r Greenwich Royal Obfervat. 
J St. Paul’s Church 
b Limehoufe Church 

3 1 5 3 8 

27 52 40 

1 21. I 42 

f from Limehoule f 
l Church 1 

1 3999-3 
15402 


N° 


the 'Trigonometrical Operation. 


2 57 


• CO 

G p 

cr* & 

*— » £^4 

N° 

Triangles. 

Angies. 

Diftance of the ftations from 
the interfered obje£t in feet. 

CJ *-* 

6 *2 
o ^ 
c -T 3 . 

2 ^ eh 
p oo d 

c 3 +-| 

o c *-i 

_C c 3 

(<• 0.5 1 

f 

r 

27. < 

r Argyll Street Obfervatory 
St. Paul’s Church 
S.W. pinnacle of the S. tower 
of St. Peter’s Ch. Weftm. 

0 t n 

01 47 27 
39 42 24.5 

78 30 8,5 

| from St, Peter’s [ 
J Church, Weftm. [ 

6279.5 

8661.8 

cti tp, JL U C 

_ 

- 

Norwood 

? 8 s 5 

1 from the Menu- j 

36409.7 

Great ii 
and Arg 
Street i 
ftrume 

28. * 

Argyll Street Obfervatory 
The Monument 

64 9 55-7 
97 44 59-3 

J ment [ 

I2 557-5 

2 -H f 


Jew’s Harp ftation 

52 52 53 

| from St. Paul’s j 

13522.0 

IS .y . 

P- 1 c 


Black Lane ftation • 

92 12 30 

J Church { 

10790.3 

X c a J 

> O fi 1 
c «-i ] 

j 3 O "2 | 

29. < 

St. Paul’s Church 

34 54 37 

from Jew’s Harp tr 
Black Lane, the baft 

b 5 1 

W ts cr 1 v 

■* 



of 1783 

7744-3 

t* -cj r 

z .t: 

r 

[Jew’s Harp ftation 

89 56 55.9 

j from Argyll Str. j 

5656.8 

CO > 

T* ' U Z 
<U C 

op x 5 

3°. - 

V- 

Black Lane ftation 
\ Argyll Street Obfervatory 

■36 9 50 

53 53 J 4 -i 

9586.2 

< o b 

Co 

<D 'D p l 

r 

Argyll Street Obfervatory 

95 3 ° 56-5 

1 from the Britifh f 

3488.3 

-g cr j 

*-»■*-* v 

21 J 

Jew’s Harp ftation , 

30 5 26 

j Mufeum \ 

6514 

s 

3 1 

Wind Vane of the Britijk 




• r— < •— < • E 

^ « r ! 

j_, o i 
(U ti C I 

V 

Mufeum 

54 23 37.5 


\ 

. — . C! u 

&Q <o p 

£ B<a 

f 

Argyll Street Obfervatory 
Jew’s Harp ftation 
Charlotte Street Chapel 

74 26 16.6 

1 from Charlotte J 

1848.I 

One ; 
inftru 
the a 

32. < 

V 

19 r 55.9 
80 31 47.5 

J Street Chapel { 

5459-4 

i r 

f 

Jew’s Harp ftation 

85 27 45 

) from Portland J 

4097.7 

c 

o 

u 

cS 

re 

33 * * 

V 

jBlack Lane ftation 
I Portland Chapel 

28 53 3 ° 
6 5 38 45 

/ Chapel { 

8474.2 

t) co ' 
-a oo 

*"* i>. 

f 

Jew’s Harp ftation 

60 43 55 

J from Fitzroy J 

4 OI 5*5 

• -* uj 

* C 

7 « "1 
r! 03 

34. [ 

Black Lane ftation 
Fitzroy Chapel » 

3 1 J 2 45 
88 3 20 

j Chapel J 

r 

6759.6 

r 

Jew’s Harp ftation . 

63 25 50 

1 from the Taber- J 

4780.8 

=3 

xi cr 
° _ 
to w 
(U o 

35 - j 

V 

Black Lane ftation 
7 abernacle . 

37 *4 4 ° 
79 *9 3 ° 

J nacle. 

7048.4 

angl 

mi 

{ 

Jew’s Harp ftation 

19 45 45 

| from the Small- 1 

6670.5 

X 

36- h 

Black Lane ftation 

56 57 45 

J Pox Hofpital J 

2690.4 

o 

pq e 

1] 

Small- Pox Hofpital 

lOg l6 3O 

k 


Vol. LXXX. L 1 N° 


iierved with the aft.j 
[quadrant in 1783. 


258 


• Gen . Roy's Account of 


1 

N° 

Triangles. 

\ 

Angles. 

Diftances of the ftations from 1 
the interfered object in feet. 

t 

\ 


f ;Tew’s Harp ftation 

0 / // 

4 4 1 45 

1 from St. Fancras f 

5728.1 

■w. 

37 - ■ 

2 (Black Lane ftation 
l_iS U. Pane* as Cbnrcb 

12 58 25 

l62 I9 5O 

j _ Church 1 

. 

2088.8 


That thefe fecondary triangles may be more generally ufeful 
to the inhabitants of London and its environs, the angles, 
which the 53 points comprehended in Plate XI. refpe&ively 
form with each other at the center of the dome of St. Paul’s, 
are colleded in the annexed table, together with their feveral 
diftances from that central point. The objedts are arranged 
into two claffes, according as they are fituated to the eaftward 
or weft ward of the meridian of St. Paul s. Thofe of the 
firft clafs commence at the north meridian, and proceed by the 
eaft to 180°. Thefe of the fecond commence at the fouth 
meridian, and^proceed, in like manner, by the weft to 1S0 0 . 
From this table the total angle between any two objedls being 
had by fimple fubtradlion, and the diftances from St. Paul’s 
given, the diftances of the objedls from each other are readily 
obtained. Whoever, therefore, fhould be defirous of know- 
ing accurately his own fituation in this great metropolis may 
eafily fatisfy himfelf, by taking two angles from the top of 
his houfe, with a good Hadley’s fextant or theodelet, be- 
tween any known objedls near to him, and thebeft dilpofed for 
the purpofe. By the help of thefe data , and a very fimple trigo- 
nometrical computation, he will obtain what he wants ; and he 
may even fatisfy another curiofity which will probably occur, 
namely, that of putting to the teft: our original operation, by 
trying how nearly different triangles bring out the fame refult. 
It will readily be conceived that, for trials of this fort, the 

l points 


the 'trigonometrical Operation. 

points whofe fituations have been determined by the great in- 
ftrument Ihould be chofen preferably to the others ; and next 
to thefe, the obje&s that have been fixed by one angle, taken 
with the Argyll-Street inftrument, as more to be relied upon, 
than thofe obferved with the agronomical quadrant or 
fextant. 1 hus an excellent foundation is laid for the improve- 
ment of the plan of London and its environs, which may by 
thefe triangles be rendered rhore accurate than would have been 
poffible by any other mode. 


Table (hewing the bearings and diftances of objedtsl 
fituated in and near London, from the center of the 
Dome of St. Paul’s. 

_ — - — - r 


_ 

Obje&s. 

Bearings from 
the north me* 
rid. eaftward. 

Diftances 

in 

fee t. 

t 

Eaftward 
of the 
meridian { 
of 

St. Paul’s. 

1 

' Newington Church . 7 . 

St. Luke’s Church, Old Street 
St. Leonard’s Church, Shoreditch . 

The weft pediment of Wanftead Houfe 
St. Matthew’s Church, Bethnal Green 
Chrift’s Church, Spitalfields 
Bow Church, Cheaplide . 

Limehoufe Church 

St. George’s Church, Ratcliff Highway 
The Monument 

Severndroog Caftle, Shooter’s Hill 
Tranfit-room of Greenwich Royal Obferv. 
Eltham Church 
Loampit Hill 
Station at Norwood 

South Meridian of St. Paul’s 

o / // 

9 59 39-3 
12 57 53-7 
44 57 39-8 
55 53 4&-4 
59 3 1 37-3 

7° 3 8 37-3 
87 48 4.1 

92 51 6 

98 56 56.3 
ns i 5 45.7 
1 15 28 50.4 
120 43 46 
123 46 4.2 

134 40 48.7 
175 47 18.4 
180 0 0 

17641 

4262.7 

6746.4 
36308.4 

8165.8 

5878.4 s 
1078.1 

15462 

8846.4 

3 XI 4-2 

39963 

25655-5 

41091 

2345°- 1 
37841 


L 1 2 


Weft- 


Gen. Roy's Account of 


l60 


Objedls. 


IBtarings from 
the fouth me- 
Irid. weflward. 


// 


Weflward 
of the 
neridian 

of 

St. Paul’s. 


Stretham Church 

Clapham Common, Mr. Cavendish 
Batterfea Church • * 0 - 1 

St.Peter’sCh.Weflm.SWpinnacle of theb. 1 . 

Fulham Church • • 

Kew Pagoda 

Richmond, Royal Obfervatory 
St. Martin’s Church, in the Strand 
Spring Grove Houfe, Sir Jos. Banxs, Bt. 
St. James’s Church 
South Audley Chapel 
St. Mary’s, New Church in the Strand 

St. Clement’s Church 
St. Ann’s Church, Soho 
St. George’s Church, Hanover Square 
St. Bride’s Church, Fleet Street 


13 

26 

5 ^ 

52 

S 7 

7 1 

7 i 

74 

76 

77 
Si 

Si 

85 

86 
S6 
90 


Diflances 
in 

feet. 


22 

3 2 


57 7-8 

29 56.1 
27 6 
13.2 

39 44-6 
2 36 

42 O.I 
28 59.2 

9 49 3 
49 9-8 
49 4 2 -7 

57 2 7-7 

36.7 

58.7 

12.9 

42.8 


57 

9 

2 3 

12 


Argyll Street Obfervatory, Maj. Gen. Roy I 92 14 37 *; 




The Pantheon 
Hanger- hill Tower 
St. Giles’s Church 
Portland Chapel 
Charlotte Street Chapel 
St. George’s Church, B’oomfbury Square 
Wind Vane of theBritifh Mufeum 
The Tabernacle, Tottenham Court Road 
Fitzroy Chapel . • 

Harrow on the Hill Church • 

} ew ’s Harp flat ion of 1783 . 

Primroft Hill flation of 1 7 83 
Hampflead Church • 

St. Pancras Church • 

The Small-Pox Hofpital 
Black Lane flation of o 8 3 
Highgate Chapel 
Mr Du veluz’s Cupola, Hornfey Lane, High. 
Horniey FIill flation of 1788 
Iflington Church • • 

Highbury Houfe, Mr. Aubert 
Ditto, the Tranflt-room of his Obfervatory 
North meridian of St. Paul’s 


93 

94 

94 

100 

101 

103 

10 5 

107 

109 
1 12 
1 12 

I2 3 

128 

1 26 

i 37 

*47 

15° 

*55 

*73 

174 

178 

179 

180 


*9 

°4 


17.2 

. 59 6 

36 28.3 

34 3 8 -7 
30 23.9 
15 20.6 

45 45-7 
20 47 
41 10.2 

7 58-3 

58 3°-7 
28 40.8 
c6 11. 8 

43 2 5-8 
38 37-8 
53 7-7 

CQ l8. I 

27 12.8 

24 3 2 *3 
40 21.4 

43 up 

1 56.6 

o o 


3 1 ‘793-5 
| 2 45 fa 3-S 
22226 

866l.8 

i°74 6 -3 
47577-7 
c 1 04 1 . 1 

6748.6 

57 2 53-9 
8978 

1221 1. 1 

4291.6 
359 2 *4 
7753-9 

10304.5 

1 7 7 1 -7 
9632 
9066.8 

45845.2 

6917-3 

10301.4 

8500.4 

6221.1 

6701.5 

8876.2 

9559-9 

58764.2 
43522 
[17072.8 
[24148. 

10600. 
8732. 
10790. 
24062 
22646 
22297.1 

9028.2 

*4595-7 

* 45 6i -4 


Com** 


/ 


Cjo CO *0 '-J 


the Trigonometrical Operation . 


261 


Computed latitudes and Ion 

the at 

Places. 

gitudes of d 
)Ove table. 

Latitudes. 

)me of the places in 
Longitude from Greenwich 

in degr. &c. 

in time. 

St. Paul’s 

Highbury Houfe, Tranfit-room 
St. James’s Church 
Argyll Street Gblervatory 
Clapham Common, Tranfit-room 
Richmond Royal Obfervatory 

0 / // 

51 30 49.43 

S l 33 I2 - 8 
5 1 3 ° 3°-7 

5 1 3 ° 53-°5 
51 27 12.7 

51 28 7.9 

O, S /> 

0 5 40 8 

0 S 30-5 

O 8 3 

0 8 18.36 

0 8 ?g .2 

0 18 42.3 

h m fee. 

O 0 23.12 

0 0 2 3 37 

0 0 3 2 *33 
0 0 33.224 

O O 54.6 ! 3 

O 1 14.82 


CONCLUSION. 

IN the courfe of this Paper, an account has been given of 
the commencement, progrefs, and completion of an operation, 
the firft of its kind in this country, undertaken by the com- 
mand, and executed under the aufpices, of a mod: gracious and 
beneficent Sovereign, the Patron of the Sciences. 

From a liberal fupply of much better indruments than ever 
were ufed for purpofes of this fort on any former occafion, and 
every other adidance that could contribute towards fuccefs, the 
operation has undoubtedly derived fome peculiar advantages : 
for, befides a more accurate mode of meafuring the bafes than 
has heretofore been pradtifed, the angles of the triangles have 
been obferved fo truly, that the relative geodetical fituations 
of the dations, as determined by plane trigonometrical com- 
putation, may be faid to be free from fenfible error. 

The indrument too, by means of its tranfit telefcope, being 
admirably calculated for determining, with great precilion, the 
true direction of the meridians, their convergence to each 
other, and confequently the differences of longitude, have 
2 thereby 


262 Gen. Roy’s Account of 

thereby been obtained by angular meafurement alone, without 
any regard to difference of time, more or lefs erroneous even 
with the very bell: time-keepers, and not perhaps to be de- 
pended upon to nearer than half a fecond, after taking a mean of 
a number of comparifons. This mode, by angular meafure- 
ment, was fuggefted in the Paper of 1787; and we prefume 
to think, that the refult of the operation has fully verified the 
goodnefs of the method by the confiftency of the pole-ftar ob- 
fervations among themfelves. It may be laid to be a new mode 
of furveying, by the help of the pole-ftar as a fixed point, for 
preferving the accuracy of the operation, fuccefiively carried on 
from meridian to meridian ; and the fame mode ftiould be 
adhered to in future. 

Another circumftance muft likewife be noticed, as having been 
propofed at the fame time, namely, the ufe of white lights 
for the diftant ftations : for without the help of thefe, ob- 
ferved with fuch an inftrument as ours, it would have been 
utterly impoflible to have determined accurately the diftances of 
Montlambert and Blancnez, the firft nearly forty- feven, and 
the laft nearly forty- eight miles from Fairlight Down. 

Without farther recapitulation, the Writer of this Account 
cannot help confidering it as being incumbent on him to recom- 
mend, that the trigonometrical operation, fo fuccefsfully be- 
gun, fhould certainly be continued, and gradually extended 
over the whole ifland. Compared with the greatnefs of the 
object, the annual expence to the publick would be a mere trifle 
not worthy of being mentioned. In reality, a chief part of 
the expence, namely, that of fine iriftruments, has already 
been incurred ; and it would be a pity indeed to fuffer them to 
be laid up and remain ufelefs. The honour of the nation is con- 
cerned in having at leaft as good a map of this as there is of 

any 


the Trigonometrical Operation. 2 g 

any other country. Bur, by proceeding with the work in the 
iame manner as it has been begun, with more perfed inftru- 
ments than have heretofore been ufed, and feme of thefe ap- 
plied in a new way, a map of the Britilh Mantis will at length 
be obtained, greatly fuperior in point of accuracy to any that 
is now extant. 

One additional inftrument would certainly be wanted, that 
is, a zenith fedlor for the determination of the latitudes, when 
the operation came to be extended to any confiderable diftance 
from the parallel of Greenwich. But this would not be ne- 
ceflary at firft ; while fuch a one is preparing by Mr. Rams- 
DiiN, and whicn he will no doubt render the compleateft thing 
of the kind, the operation fhould be continued in the parallel 
of Greenwich, or m the perpendicular of its meridian, quite 
to the weftern fide of the ifiand in the manner following. 

In more than one place of this Paper we have had occafion to 
exprefs our regret, that the recent feries of triangles did not afford 
diftances fufficiently great between points reciprocally vifible, 
for the bell application of the pole-ftar obfervations, to the de- 
termination of the differences of longitude. It Is believed, 
that the obfervations themfelves are extremely near the truth, 
but not wholly free from error ; therefore, whatever this may 
amount to, on double or triple the diftance it would certainly 
be reduced to one-half or one-third part. 

Shooter’s Hill, and Nettlebed Heights on the eaftern fkirt of 
Oxfordfliire, are reciprocally vifible at the diftance of about 
forty-fix or forty-feven miles from each other. Nettlebed 
Heights, and a thin clump of trees on the Gioucefterlhire 
range of hills, called Paul s Ppljile, about two miles weltward 
from Frog Mill, on the left-hand fide of the road leading from 
tnence to Gloucefter, may likewife be feen from each other at 

Y 

the 


2 g Gen. Roy’s Account of 

the diftance of fifty or fifty-two miles. This laft commands a 
moft extenfive profpeft over the plain of the Severn and the 
Welch mountains to a great diftance beyond it. Pen-y-l oel 
Hill, called alfo the Sugar-loaf of Abergavenny, in Mon- 
mouthlhire, would become the third Ration to the weftward ; 
and two, or at moft three, Rations more would reach St. Da- 
vid’s Head, oppofite to Wexford in Ireland. 

But let us fuppofe, in the firft place, the feries of triangles 
to be extended only to the third ftation, in all which ipace it 
would be wholly unneceffary to obferve any latitudes ; by the 
pole-ftar obfervations, repeated a fufficient number of times on 
both fides of the pole, at each of the ftations, the length of 
the degree of a great circle, perpendicular to the meridian, 
and confequently the differences of longitude, would thereby be 
obtained to the utmoft precifion. A determination of this fort 
would abfolutely be conclufive, with regard to the length of the 
vertical and radius of the parallel in the latitudes of the refpec- 
tive ftations, afcertainable by their diftances from the perpen- 
dicular to the meridian of Greenwich. 

The fecond part of the operation would be that of carrying 
a feries of triangles fouthward from Pen y-Voei Hill, in the 
dire&ion of its meridian to the Britifh Channel; and after- 
wards extending thefe triangles in the ufual manner over the 
whole fouth part of the illand between Kent and the Land s- 

End. 

If, b elides the zenith feclor, another circular inftrument was 
provided, and fodne additional annual expence allowed, in order 
to accomplilh more fpecdily lo great and uleful a work, at the 
fame time that the operations to the fouthward were carrying 
on, the feries of triangles, in the direction of the meridian of 
Pen-y-Vocl Hill , fhouid be continued to the northward through- 


the 'Trigonometrical Operation . 



out the extent of the ifland till it fell into the Murray Frith. 
A new meridian might then be taken more to the weft ward, 
perhaps that of Inyernefs, or fome hill near it, whereby the 
feries would be extended to the North Sea, bounding the coafts 
of Sutherland and Caithnefs. 

It is unneceffary here to enter into any minute detail of what 
fliould be the fucceeding parts to be carried preferably info exe- 
cution, as things of this fort would naturally prefen t them- 
feives, in the. courfe of fuch important operations,, to thofe 
entrufted^ with the direction. It is however fufficiently ob- 
vious, that having, as above fuppofed, obtained the meafure of 
a portion of the meridian amounting nearly to fixteen degrees 
of latitude in continuity, .between' the Pyrenean mountains 
and the northern extremity of Britain, or more than one*fixth 
part of the diftance between the equator and the pole ; the 
things of the next confequence to be obtained would be, the 
meafures of the radii of the vertical and parallel in the low- 
lands of Scotland, that is, in the latitude of Edinburgh, and 
again at the northern coaft. In each of thefe fituations it is 
evident, that about three degrees of longitude might be mea- 
fured with great exadtnefs. At the north, for inftance, Cape 
Wrath being made the central ftation, from thence the Orkney 
IJlands to the eaftward and Butt of the IJland of Lewes to the 
weftward, being diftindtly feen, would confequently become the 
ftations to the right and left. 

With regard to the ufe of white lights, fo indifpen.fably ne« 
ceffary in all operations of this fort, no opportunities have yet 
offered of afcertaining with precifion the immenfe diftance to 
which they may be feen in favourable circumftances of the 
weather, and with fufficient elevation of theftations above the 
fea. Thofe commonly ufed in the recent operation were only 


Vol. LXXX. 


M m 


three 


2 66 Gen. Roy’s Account of 

three or four inches in diameter, and the largefl but fix orfeven. 
Augmented to nine or ten inches, exhibited on the top of one 
high hill, and obferved from the top of another, when there 
is no moonlight, and no rain or fog, they would probably be 
feen eighty or a hundred miles. In fhort, wherever the moft 
faint looming of the land in a very clear day can be dilcei ned, the 
lights, from their extraordinary brilliancy, would undoubtedly 
be feen in a dark night, when the air was perfectly clean 

Hence, it will readily be conceived, how eafily and accu- 
rately any trigonometrical operations that might be carrying 
on in England and Ireland at the fame time might be conneded 
with each other, by means of thefe lights, alternately exhibited 
and obferved, for in Ranee, on Brach-y-pwl Point, Holyhead 
Hill, and the Ife of Man , on one fide ; and again on the 
mountains of Wicklow, hill of HoWlh , and mountains of Mourne, 
on the other. 

In the Paper of 1787, and again in this, we have had occa- 
fion to remark on the improbability of being able to determine 
the differences of longitude, by the inflantaneous explofion of 
light, fo accurately as by angular meafurement with a fine in- 
flrument, applied as it has been 111 the recent operation. Put 
lince, undoubtedly, there will be different opinions on this 
head, it will be very proper that both modes fhould be tried, 

that the refults may be compared. 

To the eaftward of Greenwich, the Ration for explofion 
might be taken at Montlambert, Fienne Windmill, or at Folk- 
fone Furnpike, in order to render the diftance of the extreme 
Rations as great as poffible. Any of thefe points would be 
vifible from Crowborough Beacon, which would become the 
Ration of the Englifh aflronomer with his clock and inflru- 

ments. That of the French aRronomer would of courfe be 
- • taken 


the Trigonometrical Operation . 2 g 

taken in the mod convenient place inland on the range of 
chalk hills, vifible from the place of explofion, and the eafieft 
connected with the triangles of the meridian of Paris in the 
neighbourhood of Helfaui and Bouvigny. Crowhorough is about 
70 miles diftant from Montlambert, and a point in the direction 
of thefe two near Helfaut would be about 32 miles inland from 

Montlambert , which would give for the extreme diftance about 
102 miles. 

If experiments of the fame kind were to be made to the 
weitward of Greenwich, thofe very ftations, already propofed 
for the continuation of the triangular operation, would be the 
fitted: that could be chofen for the purpofe. 

Now, fuppofing the operations already mentioned in the 
parallel of Greenwich to be executed, the meridian of Pen-y- 
Voel Hill extended to the northern extremity of Scotland, and 
three degreees of longitude meafured in that latitude, while 
the Eaft India Company were carrying on operations of the 
fame nature on the coaft of Coromandel and in Bengal, every 
thing would then be done that Britain could do within her 
own dominions, in regard to the determination of the figure 
and dimenfions of the earth. If, after this, any doubts re- 
mained, thefe might eafily be removed, by Portugal’s mea- 
furing a degree or two of the meridian under the equator, and 
alfo a portion of the earth’s equatorial circnmference ; while 
fome other nation repeated the operations at the polar circle, 
or made new ones ftill nearer to the pole, if fuch Ihould be 
found practicable, all which has been fuggefted in the Paper 
of 1787. For the farther illuftration of this fubjed, it will be 
proper to refer to fig. 3. in Plate X. 

With regard to the execution of any future operation that 
may, and which it is hoped will, be hereafter undertaken in 

Mm2 " Britain, 


2 68 Gen. Roy’s Account of 

Britain, there remains but one point more to be mentioned, 
that is, the meafurement of new bales. In the execution of 
the great map of France, no fewer than feveenteen were mea- 
fured. But, with Rich inftruments as have been ufed in this 
country, a fmaller number would Riffice ; and the belt fitua- 
tions for the purpofe will naturally prefent themfelves in the 

courfe of the operations. # 

Thofe that immediately occur to the Writer ot this Me- 
moir, as likely to be found the mod proper, are the following, 

viz. 

1. On Sedgemoor in Somerfetlhire. 

2. On Boftou Fens in Lincolnlhire. 

3. On the fands on the coaft of North Wales 

between Pen man Mawr and Beaumaris, . v _ 

4. On the fands between Holy Ifland and tpnng tides. 

Berwick upon Tweed, • • * 

5 . On Kincairden and Flanders Mofs, weftward from Stir- 
ling. 

6. On the fands on the coaft of Aberdeen {hire,. 

between the mouth of the Don and Newburgh, I at low water 

7 . The fands on the coaft of Murray, between ffpnng tides. 

the mouths of the rivers Findhorn and Nairn, 

8 On the Moan morafs, inland from the Whiten Head 


at low water 


Otl 


the coaft of Sutherland. 

In the meafurement of thefe bafes, which fhould not be 
lefs than fix, but as often as poffible even eight or ten miles in 
Fngth, there would not be any neceffity for that wonderful 
exactnefs that was requifite for determining the length of the 
firft and fecond bafes on Hounflow Heath and Romney Marlh. 
Suopofing them to be executed with the fteel chain alone within 
a few feet of the truth, it would be perfectly fufficient to Ihew 


the Trigonometrical Operation . 269 

that no error of any confequence had accumulated in carrying 
on the operation to thefe diftant points refpedtively, even as far 
as the remote fhore of the Northern Ocean. 

Finally, in order to preferve the primitive fcale of diftances* 
whereon the accuracy of the recent operation, and all future 
ones that may hereafter be connected with it, muft always be 
fuppofed to depend, it is indifpenfably neceffary to eftablifh, 
without lofs of time, fome permanent marks at the extremities 
of the bafe on Hounflow Heath*. Thefe fhould be low cir- 
cular buildings, riling but a few feet above the furface of the 
Heath, compofed of the hardeft materials, fuch as granite, and 
conftru&ed in the moft durable manner by dove-tailing the 
ftones into each other. They would referable thofe bafements 
of ancient croffes we often meet with, formed into regular 
Heps, whereby the afcent is rendered eafy to the top of a 
circular table or platform, of fufficient dimensions for the re- 
ception of the great inftrument on any future occafion. 

In the interior part of thefe little buildings, metal tablets 
would be inferted, containing the name of that much-beloved 
Monarch in whofe reign the operation was begun, and thefe 
buildings executed ; the diftance from one to the other; the 
angle of the bafe with the meridian and alfo the, magnetical 
variation. 

It is not to be doubted, that the refpedtive lords of the ma- 
nors will readily veft in the Royal Society, the property of the 
two fmall fpots of the Heath fufficient for the ere&ion of thefe 

* Soon after the measurement of the bafe, Mr. Mylne, F. R. S. at my 
dehre, was fo obliging as to give a defign for a building of this kind, which, 
being conftru£fed nearly in the way of the Eddyltone Light-houfe, executed by 
the ingenious Mr. Smeaton, would anfwer very well. 


termini. 


;27© -Gen. Roy’s Account, &c. 

terminu They ifhould be carried into immediate execution ; 
for, if this bufinefs (hould be poftponed for any length of time, 
there will be danger of its being altogether forgotten. In a 
few years the wooden pipes funk in the earth will decay; and 
thus the primitive fcale of diftances, which coft fo much 
labour and expence to obtain, will be irretrievably loft. 



Errata in Phil. Trans. Vol. LXXVII. 

V *v 

1 . V > 

Page. Line. 

193. 6. from the bottom, for 133 417 read 133409 

194. 2. from the bottom, for p. 53. and 56. of the firft part read p. ixiii. 

Part Third 

196. 8. for 351. read 358.6 

IO. read 1 3341 7 

198. 3. from the bottom, dele (Si„ fannies) 

199. dele from the femicolon in line 4. to the end of the paragraph 
202. 12. for 609 read 521 

206. 3. for 27350 read- 27342 
6. for 2078 mzff 1819 

207. 9. from the bottom, for 2733 1 W 27337— L. 8. /or 1758 ^1734— 

L. 3. fur 27301 nad 27294^-L. Jt./ar 1288 rrW 1043 t 

208. 8. for 27294 27288 

9. 1177 read 934. 

16. jfar 27241 27243 

17. for exceeds the truth 202 rW falls fhort of the truth 41 

5. from the bottom, for 27230 27224 

4. f or exceeds the truth 131 read falls fliort of the 

truth 1 10 

209. 3. for 27206 read 27212 

5 * for exceeds the truth by 46 read fails fhort of the truth by 165 

210. 9. for 27295 read 27288 

10. for 1196 933 

21 1. 5. for 27243 27234 

218. from the period in L. 3. from the bottom, to the end of the page. 

1 he ak°ve errata have been given, in order to free, as far as is now poffible, 
the Paper of 1787 from the errors indicated in the Note at the beginning of 
Sedion VI. of the prefent Memoir, p. 201. ; but that Paper cannot be rendered 
io per fed as it ought to have been, unlefs fome ftieets of it are re-printed. 









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i. For the account of the Measurement of the base of verification in Romney marsh with the Steel Chain, in, the Matufn of 118 7 


E93 =©■ 


Philos. Trans. Vo/.LXXX. Tah.V. p 2 -j 2 


Arrangement of tlie Polls for eaclr Space of 100 Yards, or Length of 3 Chains . 





I 


Elevation of the Coffering for each. Chain. 



Spi 

ip ■ . 

rr 

r 


flan of the Coffering; for each Chain. 


him!’ ) ( I- j i-.-j -ml -ofii I’illi > ) 


Plan Sc Section of tlie Apparatus for the Extremities of the Chain; ScalcF/fart f the real dimensions. 







r 


— 


i A Single Eu/l \ 

Scale of Inches Jhr the Thin iiSectlifi,. 

1{< S <> 1 * a as 6 7 8 0 10 11 2^ 


lteai -End . 



General Section of the Hale. 


it la' I ;ill In n • 

ffiffh Nook Pipe 


-ar 


nSiiP 000 On 




1. 


■© Ega 





Dravviiig.-Polt . 


OOOO OOOOO OOOO 


A 



//(ffAA bok S ea Ha// 


/ jo. 


Feet 



re . 4 \ 






PLAN flievving' the lituation of the BASE of VERIFICATION measured, in ROMNEY MAllSII in the Autumn ot 1787 


I'MU. 7 hms IW. tm VI /.. ,jt. 


itfirif/nOH i 


Skttp ff(>u( 


JSi/iUu/tQH fine 


Omiruvi 


.1 (artMuntf (tuff 


(turnon* fjp 




I'a/tutn I,# 


(ifdtitifrn (>t/ff 


.Brufye 


/tun ring 


f/utr iirufyt 


Scale of Fathom * TTi 


1000 fu/Aonn 


Scale of Ten Thflrufend Feet 


XT 

i ' ZVl Yj- 



- -Ko >— 










General View of the Instrument . 







l%,/.ss T"4H, »:./ I,\XX T-t Vlll /> »;* 



Section of' the Instrument through the 
Microst 'opes, and in the direction of 
the J.res of' the Telescope*. 


Wait of the lust rumen f . 


Section <•/’ the Instrument tit right 
tingles to the former trhoir the Upper 
Telescope, with the lereljor Altitudes 
attached to it are nevert/eftk * repre 
settled m JZ/enafiott . 


Sonic of Incite; 


jf\] 

w 

U. III— 

• ^ 

jkl. . jn 

- 

ff 


0 

K 

V 

_ 
















A..'. . i.xxx i\ 


AWWMvfl 


>11 


I* runt Sec Uon *he Spnni/. tint/ 

('on ten/ Roller 


Section through one a/' the Pert - Screws , 
irhrrtlv the Inst rumen f ts levelled; and of 
the three Mahogany Planes that are under it. 


pour Sereins at 
malwgon v Plan \ 


Under side of one of the 
taehetl to the octagonal* 
for bringing the Center of the Instrument hy 
,r — the help of its plummet, oner tiny point 

i pj round. 

I 


Various parts of the Instrument represented to large Seales. 


Scale of Inches for parts represented In their 
real dimensions. 


Plan of a part of the 
Circle, with the. ClawgJV/ieels, 
Screw, and Hooks -joint, that 
gwe it a slow motion. 


Milled- head -Key placed at C. /hr 
clamping the Instrument . 


Trout Kiev aboil of one of the Pee f 
Screws, shewing likewise one t >frh, | 
Hlftics of bo.r-wood. and one of the [ 
••on leal Rollers behind it 


Section of the Top if' the vertical sins . 


Plan of one if the Pert of the Instrument 
Settle of flu real dimensions 

















- 


! 

























■ 





















' , - J5 . ■ 






' ■ 







' 

- 
















j r 




i>< \ i 


For the Explanation of the Microscopes, and Mechanism lor the Wires in the Eve-ends of the Telescopes 


\ 


V i 1 C It () S C () 1’ E. A 


1* I a n s. 

Upper or Hrifi Slolr. 

rri t ■ MB I 
\ 


E 1 c v at i on. 



(Btfr, .6. 






Plans Elevation s 



Various ARiiCLEs of Machinery used m run course of the Operation 


Trant IM 1.1X1 Tmk\\ f> 


Flagstaff . 

carrying UJeeu/iie 
H^rerbetiloiy I. amp* 


Pom able Crane 


Tripod Ladder 


Portable Scaffold 


Tripod 

for \Miilc Lightt 


Scute cf’ Ft ct J'or tfn Crane . 


(Mm/frt */e . 



















— — 






/ 









v' £$$$ 



















> 




■ 

' 

— - — 










1 .. 

, * i 

* 

- 

;; , . ■ 









PI Mil 



dVmd Vki 


Scale of Feet .for nil these Fla i 


Temerden Ch. 


Coudhurft Cli 


Frant Ch 


PLAN S. shewing the Pofition of the INSTRUMENT on fuch Towers, Steeples of Ch urches, or othe r Building s.as became STATIONS m the SERIES of TRIANGLES.^ TrilniViil Lxxx Tnk m r 


Hanger Hill Tower, 


Keep of Dover castle 


Greenwich 
Royal observatory. 




vS evemdroog Caftl e, Shooters Hill 


Swing-field Ch. 


REFERENCES. 

Tranfi t Room , oner uiiett a temporary 
Seq/fll was jilaced /or the Instrument 
Quadrant -Room . 

Afaist ants -Room . 

Telescope -Room . 

ITatform over the Octapon Room . 
Eaft Eipiatorial . 

Weft Etjuntorial . 

Wind Vane Turret '. 

C am era Turret . 

Library . 

Apartments. <n the Ihi el/tnff /louse 
Kitchin . 

Out Houses . 




Lydd Ch. 









^"fhomdcn Hall 


Htofutatc Ch ' 


Rum ford 


Shoebury 




mwich. R. Ob. Lat. 51 . 28. 40 


-, {W M 


the Meridian of Greenwich R. Ob. 


Greenwich R.J 


) /. or\ ^ Shurrufi 


\\ \ 

• OxutlAurjt 


North Fore laud 


_s-AT~- ar ga te 

tiSF' 111 ; i 

Si Peters # & 

Isle or thanet f. 


^UhitatabU' 


Ramsgate 


ftivtbam HR 


Krwckfwlt Buck*. 


CANTERBURY 


Sandwich 


lotlingbomjl ’H 


Maififtc 0 

* 


Jtvr/i/. 


sT»m bride 


Waltlervbare Mon ‘ 


South Foreland 


teacAborvu /h Su 


■Folkstcme 


Fort kever.t^ 


XLV 


Honitcote 


Graveline: 


XXXVI 


to nuuv 


XXXVIU 


:N GEN ESS 


XXXV 


Q,Brouleult 


XXX 1 U 


WaUtn 


Berliil/ 


Mont Cafsel' 


langney Fouu. 


be achy Head 


)p}iuluinbei( Sitjl 


Phi to». Trans. TV. LXXX. Tab. XI If s 7 i 


Scale of Thirty Tho uf and Fathoms- 


PLAN of the TRIANGLES whereby the DISTANCE between the ROYAL OBSERVATORIES of GREEN WICiH and PARIS has been determined 


pi i\ 




A*. 


' "Vfe.U (V:,.fv«! 


o Horsham * 

R A .V 


5 






’ ''S'? -g 




Grow bo no ugh B l 








^ ' z/ 7 v \ 

; ^ y ' c- - 

% •***-'• j5LI L* 

T “ 1 L *“■ 


Sralr nf *T~K ■ r m \t I a 


r.r 'Tt-> .1-1 TVinu Tnisi-i Ratio to the Fathoms «s io 65 . 7 5 to 1000 





For THE FIGURE OF THE EAR T/I, POLE-S TAR OBSERVATIONS, DIFFERENCES of LONG I TIDE AXl> TERRESTRIAL REFRACTIONS. 


I'li'I"' Tr.nix I ol 1. XXX.'/;/ A XIV ;yj 


K*.S. 


Fi**-. 


S' 7 













t 




' 

. 

- 






I ' 





/ 

/ 

' I 

. ■ 1 













- 










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' 


’ 












. 






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’ 





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- 











METEOROLOGICAL JOURNAL 

KEPT AT THE APARTMENTS OP THE 

ROYAL SOCIETY? 

BY ORDER OF THE 


PRESIDENT and COUNCIL.’ 


[ 2 3 


METEOROLOGICAL journal 

for January 1789. 


1789 


Jan. 


ime. 


EL M. 


Therm. 

without 


Therm, 
within. 


Barom. 


Winds. 


Weather, 


O 


2 Q, 26 


10 


HI 


12 


39 


40 


Inches. Inch. Points. |Str. 


jSWhy W 
WNW 
WNW 
WNW 


o,S2S 


w 

N by E 
N 

NNW 

E 

E by S 
SSW 
SSW 

S by W 
SW 
W 

wsw 


{Cloudy. 
Cloudy. 
Cloudy. 
Cloudy. 
Foggy. 
Cloudy. 
Cloudy. 
[Cloudy. 
Fine. 
Fine. 
Cloudy. 
Snow. 
Fine, 
[Fine. 
Fine. 
Fine. 
Snow. 
Snow. 
Snow. 
Snow. 
Cloudy. 
Cloudy. 
Fine. 
Fine. 
[Snow. 
Cloudy. 
Fair. 
Fine. 
Cloudy. 
Fair. 
Fine. 
Fair. 


M E T *S 


I 3 ] 


METEOROLOGICAL JOURNAL 

for January 1789. 


1789 

Time, 

Therm 

withoul 

Therm, 

within. 

Barom. 

Rain. 

Winds. 

- 

Weather. 

H. 

M 

0 

0 

Inches. 

Inch. 

Points. 

Str. 

Jan. 17 

8 

c 

3 ? 

46 

29,60 

0,030 

SE 

2 

Cloudy. 


2 

c 

39 

47 

29*44 


SSE 

2 

Cloudy. 

18 

8 

c 

41 

46 

28,75 


SSW 

2 

Cloudy. 


2 

0 

42 

49 

28,58 


s 

2 

Cloudy. 

J 9 

8 

0 

3 6 

48 

29,20 


w 

I 

Fair. 


2 

0 

42 

50 

29 33 


w 

2 

Fine. 

20 

8 

0 

37 

48 

29,41 

0,270 

w 

I 

Cloudy. 


2 

0 

39 

5 i 

2 9 > 5 6 


S W 

I 

Fine. 

21 

8 

0 

40 

48 

29,71 


wsw 

I 

Fine. 


2 

0 

44 

5 i 

29,78 


sw 

I 

Rain. 

22 

8 

0 

45 

5 ° 

29,6l 

0,120 

sw 

2 

Rain. 


2 

0 

47 

52 

29>65 


sw 

2 

Rain. 

2 3 

8 

0 

42 

5 i 

29,44 

°,°57 

s 

I 

Cloudy. 


2 

0 

46 

53 

2 9»34 


S by E 

I 

Cloudy. - | 

24 

8 

0 

43 

49 

29*34 


S 

2 

Cloudy. 


2 

0 

43 

53 

29*19 


S 

2 

Rain. 

25 

8 

0 

4 i 

52 

29,28 

0,158 

WSW 

I 

Fair. | 


2 

0 

46 

53 

29,41 


wsw 

I 

Fair. 

26 

8 

0 

42 

53 

29,66 

0,123 

sw 

I 

Cloudy. 


2 

0 

53 

53 

29,69 


sw 

I 

Cloudy. 

27 

8 

0 

47 

54 

29,94 


wsw 

I 

Cloudy. 


2 

0 

5 i 

55 

29,90 


sw 

I 

Cloudy. 

28 

8 

0 

46 

54 

29,78 < 

0,062 

sw , 

2 

Elain., ; 


2 

0 

52 

54 

29,83 


sw 

I 

Cloudy. 

29 

8 

0 

43 

53 

3 °> 2 3 


SW by W 

I 

Foggy. 


2 

0 

46 

54 

3 °, 3 1 


SW byS 

I 

Cloudy. 

3 ° 

8 

0 

42 

54 

3°, 33 


s 

I 

Cloudy. 


2 

0 

47 

55 

3 °, 3 ° 


s 

I 

Cloudy. 

3 1 

8 

0 

46 

54 

3 °, 2 2 


SW by W 

I 

? air. 


2 

0 

54 

56 

3°, r 4 


SW by s 

I 

Fair. 


a z 


MET E- 


t 4 2 




meteorological journal 

for February 1789. 


[Time. 

Therm.! 

without 

0 

Therm. 

within. 

Barom. 

Rain. 

|H. M. 

0 

Inches. 

Inch. 



0,205 


0,038 


Winds. 


Points. Str 


0,200 


0,041 


0,040 


0,I« 


ssw 
ssw 
ssw 
ssw 
ssw 
s bv W 
wsw 

s by W 

w 

WNW 
W by N 
W by N 
W by N 
WNW 
W 
SW byS 
W by N 
W by N 
WSW 
SW by W 
SW 
NWbyW 
NWhyW 
WNW 
W by S 
W by S 
W by S 
WSW 
SW by W 
WSW 
W by IS 


Weather. 


1 Cloudy. 
7 air. 
Fair. 
Fair. 
Cloudy. 
Cloudy. 
Fair. 
Rain. 
Fine. 
Fair. 
Fine. 
Fine, 
air. 

Cloudyo 


1 

I 

1 

1 

1 

1 

1 

I 

I 

1 

I 

1 

1 

2 
2 
2 

I 


air. 
Rain. 
Fine, 
air. 
ine, 
air. 
Fair. 
Cloudy* 
Fair. 
Fair. 
Cloudy. 
Cloudy. 
Cloudy. 
Cloudy. 
Cloudy. 
Cloudy. 
Fine. 



M E T & 


1 


[ 5 ] 




METEOROLOGIC 

A L J 

0 U R N A L 





for February 1789. 




( 

Time. 

I" 

Therm 

Therm 

\ 

Barom. 

Rain. 

Winds. 


1789 



without 

within. 





Weather. 

H. 

M. 

0 

0 

Inches. 

Inch. 

Points. 

Str. 


1 j f 

Feb. 17 

8 

0 

3 6 

5°>5 

30^34 


SW 

1 

Cloudy. 

18 

2 

8 

0 

44 

52 

30,1° 

■ 

wsw 

2 

Cloudy. 

0 

44 

5 1 

3 °, 11 


W by S 

2 

Fair. 


2 

8 

0 

50,5 

53 

3 °> JI 


W 

2 

Cloudy. 

*9 

0 

46 

5 i 

30,00 


SW 

I 

Cloudy. 

20 

2 

8 

0 

5 * 

53 

29,91 


SW byS 

2 

Cloudy. 

0 

39 

53 

3°>°9 


E 

I 

Fair. 


2 

0 

44 

55 

3 °, 11 


E 

I 

Fair. 

21 

8 

0 

42 

52,5 

29,66 

0,141 

ssw 

2 

Rain 


2 

0 

48,5 

55 

29,59 


SW 

2 

Fair. 

22 

8 

0 

46 

53 

29,16 

0,100 

SW by S 

2 

Cloudy. 


2 

8 

0 

47,5 

55,5 

29,33 


SW 

2 

Fair. 

23 

0 

42 

52,5 

29,72 

°>i 55 

SW 

2 

Cloudy,. 


2 

8 

0 

4 5?5 

54 

29,5! 


S 

2 

Cloudy*, 

24 

0 

38,5 

49 

29,39 

<V 53 

SSW 

2 

Fine. 

25 

2 . 
8 

0 

48 

52,5 

2 9>39 

SW 

2 

Cloudy. 

0 

4 I >5 

5 1 

29,18 

0*055 

S by W 

2 

Cloudy. j 


2 

8 

0 

45,5 

54 

28,65 


SW 

2 

Cloudy. 

20 

0 

37,5 

5 1 

28,69 

0,195 

WSW 


ilain. 

27 

2 

8 

0 

41 

53,5 

28,90 

wsw 

2 

Cloudy. 

0 

39 , 

5°, 5 

2 9>55 

0,127 

WNW 

2 

Cloudy. 

28 

2 

0 

0 

4 3,5 

53 

29,58 


N 

I 

Cloudy. 

0 

0 

3 8 

51 

2 9>73 


NNE 

2 

Cloudy. 


2 

0 

42 

52 

29,84 


N by E 

2 

Cloudy. 1 j- 


METE 


[ 6 ] 


METEOROLOGICAL journal 

for March 1789. 


Therm. (Therm JBarom. I Rain, 



Winds. 


Weather 

Points. S 

tr. 

NNE 

1 ( 

Cloudy. 

NNE 

1 

Cloudy. 

NNE 

1 

Cloudy. 

N 

I 

Cloudy. 

NNE 

1 

Fair. 

NNE 

1 

Cloudy. 

NF 


Fair. 

NE 

1 

Cloudy. 

NE 

1 

Cloudy. 

NE 

1 

Cloudy. 

NE 

1 

Cloudy. 

NE 

1 

Cloudy. 

NE 

1 

Fair. 

NE 

1 

Cloudy. 

N 

1 

Snow. 

N 

I 

Cloudy. 

WNW 

1 

Cloudy. 

WNW 

1 

Fine. 

NWbyW 

2 

Fine. 

NWbyN 

2 

Fine. 

E 

I 

Cloudy. 

E 

2 

Cloudy. 

N 

I 

Fair* 

NW 

I 

Fair. 

E 

I 

Snow. 

W 

I 

Fair.. 

5 SW by S 

I 

Cloudy. 

SW byS 

I 

Rain. 

'5 E 

I 

Cloudy. 

E 

I 

Rain. 

'S E 

2 

Rain. 

NE by l' 

2 

Cloudy. 


M E T Bp 


[ 7 ] 




M E T E 0 R 0 

LOGICAL J 

for March 1789. 

0 u 

R N A L 


Time. 

I Therm. 

I herm. 

jBarom. 

Rain. 

VV liids. 





without 

within. 






T *7 8rv 





1 




„ T . , 

1 7 °9 







ii 11 11 1 


V* 


H. M 

0 

0 

Inches. 

Inch. 

Points. 

Str. 


Mar. 17 

7 

c 

32,5 

46 

29,82 


NE 

1 

Cloudy. 


2 

c 

37.S 

48 

29,82 


sw 

1 

Cloudy, 

28 

7 

c 

33,5 

44*5 

29,3s 

0,036 

SSE 

2 

Rain. i 


2 

c 

35,5 

47 

2 9 > 3 ° 


ESE 

I 

Rain. 

19 

7 

0 

34,5 

45 

29,64 

0,043 

E 

I 

Fair. 


2 

0 

40 

47 

29>74 


E 


Cloudy. 

20 

7 

0 

35 

46 

29,66 


ssw 

I 

Cloudy. 


2 

0 

42 

49 

2 9 >S° 


sw 

I 

Rain. 

21 

7 

0 

35 

47 

2 9»54 

0.394 

W by S 

I 

Fine. 


2 

0 

4 &-s 

5 ° 

29,61 


W 

I 

Fair. 

22 

7 

0 

38 

47>5 

2 9 > 3 ° 

0,180 

E 

I 

Cloudy. 


2 

0 

46,5 

50,5 

29,22 


SE by S 

I 

Rain. 

23 

7 

0 

3 6 

48 

29,70 

0,3c) 1 

NW 

I 

Cloudy. 


2 

0 

38 

50 

2 9.93 


N 

I 

Cloudy. 

24 

7 

0 

29 

47>5 

3°>°3 


E 

I 

Cloudy, 


2 

0 

38,5 

51 

29, q6 


SE 

I 

Fair. 

25 

7 

0 

33 

47 

29,50 


E 

2 

Cloudy. 


2 

0 

34 

49 

29,41 


E 

I 

Snow. 

26 

7 

0 

32,5 

46-5 

29.73 

0,010 

NE 

I 

Cloudy. 


2 

0 

3 8 >5 

49 

29,87 


NE 

I 

Cloudy. 

27 

7 

0 

2 9 >S 

4 6 ,5 

29,99 


WNW 

I 

Hazy. 


2 

0 

38 

49 

29,96 


SW 

I 

Fair. 

28 

7 

0 

34>5 

47 

29.78 


SE by S 

X 

Hazy. 


2 

0 

37 >5 

48,5 

29,69 


S by E 

I 

Cloudy, 

29 

7 

0 

35 

47 

29*57 


E 

I 

Foggy. 


2 

0 

38.5 

49 

29,62 


E 

I 

Cloudy. 

3 ° 

7 

0 

33 ’ 5 

46,5 

29,93 


NNW 

X 

Fair. 


2 

0 

41 

49 

30,00 


NW 

I 

Cloud}'. 

3 1 

7 

0 

3 6 

4 6 >5 

30,00 


W 

I 

Fine. 


2 

0 

45»5 

49>5 

29,96 


WNW 

I 

Cloudy. 


/ 


METE 


[ « ] 



/ 


METEOROLOGICAL JOURNAL 

for April r 78^ 


Q 

1789 

Time. 

Therm 

without 

Therm. 

within. 

iBarom, 

Rain. 

Winds. 

Weather. 

/ 

IT. 

M. 

0 

O 

Inches. 

inch. 

Points. 

Str. 

April 1 7 

7 

0 

48 

5 & 

29*49 

0,144 

SW by S 

2 

Rain. 


2 

0 

58 

59 

2 9>54 


SW 

2 

Fair. 

18 

7 

0 

46 

56 

29,62 

0,040 

WSW 

2 

Fine, 


2 

0 

57 

59 

29,62 


WSW 

2 

Fair. 

• *9 

7 

0 

45.5 

55,5 

29,78 


WSW 

I 

Cloudy. . 


2 

0 

5 6 .5 


29,85 


WSW 

I 

Cloudy. 

20 

7 

0 

46 

55 

3 °. 12 


WSW 

I 

Fine. 


2 

0 

6l 

61 

30,12 


WSW 

I 

Fine. 

21 

7 

0 

5 *.S 

57,5 

30,18 


WSW 

I 

Cloudy, 


2 

0 

61,5 

6o ,S 



WSW 

I 

Cloudy, 

22 

7 

0 

5 ° 

57 

3°>°5 


WSW 

1 

Fine. 


2 

0 

62 

60 

3 °, 11 


WSW 

I 

Fair. 

23 

7 

0 

4 6 »S 

56 

29,82 

0,045 

SW 

I 

Rain. 


2 

0 

56 

59 

2 9>73 


SW 

I 

Cloudy* 

24 

7 

0 

46 

56,5 

29, 48 

0,025 

WNW 

2 

Cloudy, 


2 

0 

56 

60 

29,74 


WNW 

I 

Fair. 

25 

7 

0 

44 

56 

29,84 


SWbyW 

I 

Fair. 


2 

0 

57 

59 

29,70 


SW 

I 

Cloudy. 

26 

7 

0 

4 - 2)5 

56 

2 9>33 

0,085 

SSW 

2 

Fine. 


2 

0 

5 i >5 

58 

29,27 


SW 

2 

Cloudy. 

27 

7 

0 

44 

55.5 

29,24 

0,091 

SW 

2 

Fine. 


2 

» 0 

50 

56 

29,26 


SW 

2 

Cloudy. 1 

28 

7 

0 

46 

54 

29,50 

0,049 

SWbyW 

2 

Fair. 


2 

0 

55 

57 

29,59 


WSW 

2 

Fair. 

29 

7 

0 

45 

55 

29,68 


WSW 

I 

Fair. 


2 

0 

55>5 

58 

29,67 


SW by S 

I 

Fine. 

30 

7 

0 

43>5 

54,5 

29,74 


E 

I 

Fine, 


2 

0 

57 

58.5 

29,72 


E 

I 

Fine. 


< 


Vol. LXXX. 


METE 


[ 1 ° ] 


I 



METE 



£ » I 


1 


METEOROLOGIC 

for May 

A L JO 
1789. 

U R N A L 

1 

Time 

Therm 

, Therm 

. Barom. 

Rain 

Winds. 


1 



withou 

t within, 






1 1*700 










j 4 / u y 









Weather. 


H. 

M 

* 0 

0 

Inches. 

Inch. 

Points. 

Str, 


jMay i ' 

7 

c 

5 55 

61 

29,92 

0,115 

SSW 

2 

Cloudy. 


2 

c 

> 53,5 

61,5 

29,84 


SSW 

! 2 

Cloudy. 

iE 

7 

c 

52 

60 

29,72 

0,055 

SSW 

2 

Cloudy. 

1 

2 

c 

55 

60 

29*85 


wsw 

2 

Cloudy. 

19 

7 

0 

47 

5 8 

30,22 


w 

2 

Fine. 

1 

2 

0 

59 

59>5 

'■30,27 

* 

w 

2 

Fair. 

20 

7 

0 

50,5 

59 

30,16 


E 

I 

Fine. 

I 

2 

0 

61 

60 

■ 3 °>° 4 


SE. 

I 

Fine. 

21 

7 

0 

5 ^ 

58,5 

29,90 


E 

I 

Cloudy. 

I 

2 

0 

55 

58 

29,90 


E - 

I 

Rain. 

22 

7 

0 

54 

58,5 

29,89 


SSE 

I 

Fair. 


2 

0 

58 

59 

29,87 


S by W 

1 

Cloudy. 

23 

7 

0 

55 

58,5 

29,91 

0,165 

SSW 

I 

Fair. 

1 ' 

2 

0 

63 

60, s 

29,96 


SSW 

I 

Fine. 

24 

7 

0 

56 

59,5 

29,78 

0,137 

E 

I 

Cloudy. 


2 

0 

66 

6 *, 5 

29,69 


E 

I 

Cloudy. 

25 

7 

0 

60 

6°, 5 

2 9>57 


E 

I 

Cloudy. 


2 

0 

65 

S 5 

29,59 


ESE 

I 

Cloudy. 

26 

7 

0 

5 8 

61 

29,67 


ESE 

I 

Fine. 


2 

0 

64 

62 

29,64 


ESE 

1 

Fair. 

27 

7 

0 

55 

6l 

29,67 


, s 

I 

Cloudy. 


2 

0 

62 

62 

29,70 


s 

I 1 

?air. 

28 

7 

0 

54 

6l 

29,89 


SSW 

I ( 

Cloudy. 


2 

0 

62 

62 

29,89 


SW byS 

I 1 

7 air. i 

29 

7 

0 

55 

61, 5 

29,74 < 

3,025 

SW 

2 ( 

Cloudy. 


2 

0 

61 

62 

29,74 


SSW 

I I 

7 air. 

3 ° 

7 

0 

55 

6l 

29>73 


s 

2 I 

? air® 


2 

0 

60 

6 i >5 

29,67 


s 

I c 

Cloudy. 

3 £ 

7 

0 

1 4 

60 

29,57 < 

1,321 

SW 

I I 

? air. ! 


2 

0 

60 1 

6i >5 

29,60 1 


SSW 

2 C 

Cloudy. j 


b 2 


METE 


[ I* ] 


meteorological journal 

for June 1 7S9. 


[Time. 


Therm.) Therm 
without within. 


1789 


M. M. 


June 


A 7 

2 

7 

2 

7 

2 

7 
2 

7 

2 

7 

2 

7 

2 

7 


3 

4 I 

5 

6 


8 


o 

o 

o 

o 

o 

o 


Barom. I Rain. 


2 

7 

2 

7 

2 

7 

2 

7 

2 

7 

2 

14 I 7 

2 

7 

2 

j6 | 7 
2 


10 


11 


12 


12 


o 
o 
o 
o 

°] 
o 

o 

o 

o 

o 

o 

o 

o 

o 

0 

0 1 

°i 

o 

o 

o 

o 

o 

o 

o 


54 

59 
52 
66 

55 
b 3 

52 

54 

53 

54 
53 
58 

53 

60 

50 

62 

57 

64 

54 
64 
56 
66 


Inches. Inch. 


54 
63>5 
53 
6i,5 

5° 

53 

55 
68 

62 

7*>5 


60 
60,5 
60 

61, s 

60, s 

61 , s 

60 
60 
60 
59>5 

58*5 

59.5 
59 

59.5 

58.5 

59-5 

59.5 
59.5 
5 a <5 

59.5 

59 

60.5 

5 8 >5 

60 

58 
60,5 
58 
60 
58 
62 
60 


Winds. 


Points. [Str. 


29,70 \ 0^22 2 

29,7° 

29,86 
29,86 
29,89 

29,78 1 
29,40 jo, 300 

29,4° 

29,51 [0,280 
29,72 

29,77 [0,062 
29,74 
2 9>93 
29,99 

3 °> 16 

30, 1 6 

3°, n 

30,04 , 

29,96 '0,060 
29,99 
3°,°9 

3°, 1 2 
3°, 22 

30.22 

30.23 

3 0>2 3 
3 0 ) 1 ! 

30,1° 

3°»°3 
29,98 
29,87 
29,81 


svv 
sw 
wsw 

WNW 

wsw 

wsw 

wsw 

WNW 

w 
■ w 
w 

WNW 
NW 
NNW 
NW 
WNW 
WNW 
WNW 
NW 
E 

ENE 
ENE 

ene 

ENE 
ENE 
N 
NE 
ENE 
E 
E 
E 


Weather. 


2 

1 

I 

1 


I 

I 

1 

1 

1 

2 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
1 
I 
I 
1 


Fair. 

Cloudy. 

Cloudy. 

^ine. 

Mne. 
Cloudy. 
7air. 
Rain. 
Cloudy. 
Cloudy. 
Cloudy. 
Cloudy. 
Cloudy. 
Cloudy, 
Fair. 
Fair. 
Cloudy. 

air. 
7air. 
!?air. 
Cloudy. 
Cloudy. 
Cloudy. 
Cloudy. 
Cloudy. 
Fair. 
Cloudy. 
Cloudy. 
Cloudy. 
Fine. 
Fine. 
Fine. 


mete 


[ >3 3 



Meteorological journal 

for June 1789. 


! 7 8 9 

Time. 

Therm. 

without 

Therm. 

within. 

pd 

0 

5 

e 

Rain. 

Winds 

7 ~] 

Weather. 

- 

H. 

M. 

0 

0 

Inches. 

Inch. 

Points. 

Str. 

June 17 

7 

0 

62 

6 3>5 

29.79 


E 

2 

Fine. 


2 

0 

72 

64 

29,81 


S by E 

X 

Fair. 

18 

7 

0 

62 

64 

29,88 


E 

X 

Cloudy. 


2 

0 

64 

64 

29,80 


SE 

I 

Rain. 

*9 

7 

0 

58 

6 4 v 

29,85 

0,320 

SW by S 

1 

Fine. 


2 

0 

70 

6S 

29,80 


S 

X 

Fine. 

20 

7 

0 

60 

64 

29,63 

0,116 

SSW 

2 

Cloudy. 


2 

c 

66 

66 

29,70' 


SW 

2 

Fair. 

21 

7 

0 

58,5 

64,5 

29,70 


SSW 

1 

Fair. 


2 

0 

68 

66 

29,55 


SSE 

1 

Cloudy* 

22 

7 

0 

54 

6 3 

29,45 

0,286 

s 

2 

Rain 


2 

0 

60 

63.5 

29,40 


s 

2 

Cloudy,. ' 

23 

7 

0 

54 

6 3 

29,53 

0,143 

SW 

2 

Fair. 


2 

0 

62 

6 3 

29,53 


SW 

2 

Rain, 

24 

7 

0 

55 

62,5 

29,55 

0,246 

SW 

I 

Cloudy. 


2 

0 

6x 

6 3 

29,52 


s 

I 

Cloudy® 

2 5 

7 

0 

54 

61,5 

29,60 

0,690 

E 

X 

Cloudy* 


2 

0 

60 

62 

29,64 


SW 

I 

Cloudy® 

26 

7 

0 

53 

61 

29,77 

0,242 

w 

I 

Fair. 


2 

0 

60 

62 

29,83 


w 

X 

Fine, 

27 

7 

0 

53 

61 

29,93 


wsw 

I 

Fair. 


2 

0 

59 

61 

29,87 


SW by S 

I 

Cloudy 9 

28 

7 

0 

5 ° 

60 

29' 7 1 

0,130 

w 

2 

Cloudy^ 


2 

0 

s 8 

60 

29,78 


W by S 

2 

Cloudy© 

29 

7 

0 

52 

59,5 

29,91 

0,070 

W by N 

I 

Cloudy. 


2 

0 

57 

60 

29,91 


WNW 

I 

Fine. 

3 ° 

7 

0 

54,5 

59-5 

30,00 

0,0X0 

— w 

X 

Cloudy® 


2 

0 

61,5 

6O 

30,04 


NNW 

I 

Fair. 


METE- 


/ 


[ 14 ] 



mete- 


[ *5 ] 




METEOROLOGICAL JOURNAL 

for July 1789. 


1789 

Time. 

-Therm 

withou 

. Therm, 
t within. 

Tarom. 

Kain. 

vv mds. 

1 

Weather, 

H. M 

0 

0 

Inches. 

Inch. 

Points. 

IStr. 

Jjuty 17 

7 

c 

56 

63.5 

29,64 

0,040 

S 

I 

Fair. 

I 

2 

c 

67 

64 

29,64 


SW by S 

2 

Cloudy. 

18 

7 

c 

55 

6 3 

29, 7 1 


WSW 

I 

Cloudy, 

1 

2 

0 

69 

64 

29,70 


SW 

I 

Fine. 

19 

7 

0 

57 

63 

29,71 


SSW 

I 

Fine. 

J 

2 

0 

7 i 

64,5 

29,71 


s 

I 

Fair. 

20 

7 

c 

60 

64 

29,85 




Hazy. 

1 

2 

c 

69 

65 

29,87 




Cloudy. 

21 

7 

0 

60 

64 

29,96 




Fine. 

1 

2 

0 

70 

6 5 

29*94 


SSW 

I 

Cloudy. 

22 

7 

0 

58 

64 

29*74 

0,376 

SSW 

2 

Fair. 

1 

2 

0 

62 

6 4,5 

29,70 


SSW 

2 

Cloudy. 

23 

7 

0 

56 

*> 3>5 

29,63 

0,060 

WSW 

I 

Cloudy. 

1 

2 

0 

62 

6 3 >S 

29,68 


WSW 

I 

Cloudy, 

24 

7 

0 

53 

6 3 

129,87 

0,058 

WSW 

I 

Fine, 

I 

2 

0 

6 3 

63 

29 86 


SW 

I 

Cloudy. 

25 

7 

0 

56 

6 3 

29*83 


SSW 

I 

Cloudy. 


2 

0 

62 

63 

29,78 


SSW 

I 

Cloudy. 

26 

7 

0 

5 « 

63,5 

2 9>75 


w 

I 

Cloudy. 

1 

2 

0 

67 

6 4,5 

29.78 


WSW 

I 

Fine. 

27 

7 

0 

57 

6 3>5 

29,78 


WSW 

I 

Hazy. 

I 

2 

0 

6 9 

6S 

29,78 


w 

I 

Hazy. 

1 28 

7 

0 

57 

63.5 

29,86 

0,050 

WNW 

I 

Cloudy.^ 


2 

0 

67 

6 4 >S 

29,99 


NW 

2 

Cloudy, 

29 

7 

0 

55 

63.5 

30,07 


w 

I 

7 ine. 

j 

2 

0 

7 i 

6 5 

30,00 


w 

I 

Hazy. 

30 

7 

0 

58 

64 

30,08 ( 

3,048 

w 

I 

7 air. 


2 

0 

70 

65 

30,08 


WNW 

I 

7 air. 

31 

7 

0 

57,5 

6 3>5 

30,01 


WSW 

I 

Cloudy, 

* 

2 

0 

68 

64,5 

29,85 


s 

I 

Tain. 


METE 


[ 1 * ] 



\ 


C *7 1 


METEOROLOGICAL JOURNAL 

for Auguft 1789. 


1 789 

Time. 

Therm. 

without 

Therm. 

within. 

Barom. 

Rain. 

Winds, 

Weather. • 

H. 

M. 

0 

0 

Inches. 

Inch. 

Points. 

Str. 

lug. 17 

7 

0 

58,5 

64.5 

3°> 2 5 

0,147 

N 

2 

Fair. 


2 

0 

70 

68 

3°> 2 7 


N 

2 

Cloudy. 

18 

7 

0 

60 

64,5 

3°, 33 


NNW 

I 

Fair. 


2 

0 

68,5 

67 

3 °’ 3 ° 


ENE 

I 

Fine, 

19 

7 

0 

59 

64,5 

30,26 


NE 

I 

Cloudy. 


.2 

0 

69 

68 

30^7 


E 

I 

Fair. 

20 

7 

0 

63 

66 

29,97 


E 

I 

Fair. 


2 

0 

73 

6 9 »S 

29*86 


E 

I 

Fair. 

21 

7 

0 

6 3 

66,5 

2 9?73 


W 

I 

Cloudy. 


2 

0 

68 

68,5 

29,70 


w 

I 

Fair. 

22 

7 

0 

56 

64,5 

29,70 

°,343 

w 

I 

Fair. 


2 

0 

62,5 

67 

29,76 


wsw 

I 

Fine. 

23 

7 

0 

53 

62 

29,92 

0,438 

w 

I 

Fine, 


2 

0 

6 3 

65 

29,98 


w 

I 

Fair. 

24 

7 

0 

59 

63,5 

30,14 


sw 

I 

Fine. 


2 

c 

66 

6 5 

30,16 


sw 

i 

Cloudy, 

25 

7 

0 

60 

65 

30,18 


wsw 

1 

Fair. 


2 

0 

66 

65,5 

3 °>* 5 


sw 

1 

Fair. 

26 

7 

0 

58 

64 

3°, 10 


sw 

1 

Fair. 


2 

0 

66 

6 4 ,S 

3 0 . 11 


sw 

1 

Cloudy. 

27 

7 

0 

52 

64 

30,10 


sw 

1 

Foggy. 


2 

. 0 

6 3 

66 

30,1° 


sw 

1 

Fair. 

28 

7 

0 

54 

64,5 

3°-°3 


ESE 

1 

Fine. 


2 

0 

66 

66,5 

29.95 


ESE 

1 

Cloudy. 

29 

7 

0 

60 

6S 

29,84 


E 

1 

Fine. 


2 

0 

74 , 5 

69 

29,72 


SSE 

2 

Fine, 

3 ° 

7 

0 

60 

66 

29.73 




Cloudy, 


2 

c 

67 

67 >S 

29,72 




Cloudy. 

3 1 

7 

0 

5 ? 

66,5 

29,70 

0,5x6 


' \ 

Cloudy. 


2 

c 

68 

68 

29,70 


SSE 

I 

Cloudy. 




Vol. LXXX. 


c 


METE 


[ >8 ] 


METEOROLOGICAL journal 

for September 1789. 


1789 ■ 

: 

Time. 

rherm. 
vlthout ^ 

rherm. 1 
within. 

3arom. 

Rain. 

Winds. 


H. M. 

0 

o 

nches. 

mch. 

Points. S 

>tr. 

Sept. 1 

7 

0 

57 

66 

29,69 

0,465 

SE 

1 R 


2 

0 

66,5 

66,5 

29,66 


ESE 

2 C 

2 

7 

0 

57 

66 

29.57 

0,295 

SSE 

i F 


2 

0 

66 

67 

29,58 


S by W 

2 F 

2 

7 

0 

58 

66 

29.57 


ESE 

2 F 


2 

0 

7 ° 

67 

29,48 


E 

2 C 

4 

7 

0 

58 

6 S,S 

2 9>37 

0,197 

SE 

2 F 


2 

0 

58 

65,5 

29,42 


S 

2 ( 

5 

7 

0 

57 

65 

29.73 

0,140 

SW 

2 I 


2 

0 

64 

67 

29,80 


SW 

1 1 

s 6 

7 

0 

58 

65 

29,92 


wsw 

1 ( 

1 

2 

0 

65,5 

66,5 

29,96 


wsvv 

1 

7 

7 

0 

58,5 

65 

3°>°3 


wsw 

1 


2 

0 

6 5 

67 

3°>°3 


wsw 

1 

8 

7 

0 

58 

65 

30,09 


wsw 

1 


2 

0 

65 

66,5 

3°, u 


wsw 

1 

Q 

7 

0 

58 

t> 4,5 

3°. 1 5 


wsw 

2 

J 

2 

0 

6 7 

66,5 

3 °> i 5 


wsw 

2 

10 

7 

0 

59 

65 

20,00 


wsw 

1 


2 

0 

74 

68 

29,88 


wsw 

1 

1 1 

7 

0 

59 

67 

29,90 

0,150 

W by N 

1 


2 

c 

61 

67 

30,06 


W by N 

2 

12 

7 

0 

5 1 

6 4 ,S 

3 °’ 3 6 

0,020 

WNW 

1 


2 

0 

> 64,5 

66 

30,38 


WNW 

1 

IQ 

7 

0 

56 

65 

30,25 


SW 

1 


£ 

0 

64 

6 5.5 

30,17 


SW 

1 

14 

7 

0 

56 

6 4.5 

29^2 


WSW 

1 


2 

0 

61 


29,80 


wsvv 

1 

I c 

7 

0 

48 

62.5 

29?82 

0,200 

W by N 

1 


2 

c 

57 

62 

29*76 


WSW 

1 

I it 

> 7 

c 

48 

59 

29.74 


WNW 

2 


2 

c 

55 

61,5 

29?78 


WNW 

I 


Weather. 


Rain. 
Cloudy, 
air. 
air. 


Cloudy. 

Cloudy. 

Rain. 

Fine. 

Fine. 

Fair. 

Fine. 

Fair. 

Cloudy. 

Cloudy. 

Fine. 

Cloudy. 

Cloudy. 

Fair. 


METE 


[ *9 1 


METEOROLOGICAL JOURNAL 

for September 1789. 


1789 

Time. 

Therm, 

without 

(Therm. 

within. 

Barom. 

Rain. 

Winds. 

Weather. 

H. 

M. 

0 

© 

Inches. 

Inch. 

Points. 

Str. 

Sept. 1 7 

7 

0 

45 

59 

29,90 

0 

V# 1 

Ml 

0 

Crx 

NWbyW 


Cloudy. 


2 

0 

54 

60,5 

29,92 


NW 

2 

Fine. 

18 

7 

0 

45 

58,5 

29.77 


W 

I 

Cloudy., 


2 

0 

58 

59 

2959 


w 

I 

Cloudy* 

l 9 

7 

0 

47 

58 

29,38 


w 

I 

Fine. 


2 

0 

56 

60 

29 > 3 ° 


WNW 

I 

Fine. 

20 

7 

0 

5 1 

59 

29.34 

o^SS 

N 

I 

Rain. 


2 

0 

57 

60 

29.43 


NW 

I 

Cloudy. 

21 

7 

0 

5 ° 

59 

29,80 


N 

I 

Cloudy. 


2 

0 

s 8 >s 

60 

29,89 


N 

I 

Fine. 

22 

7 

0 

5 ° 

58.5 

30,08 


NNE 

I 

Cloudy. 


2 

0 

60 

60 

30,05 


N 

I 

Cloudy. 

n 

7 

0 

54 

58,5 

30,00 


N ■ 

I 

Fair. 


2 

0 

60 

59,5 

30,05 


NW 

I 

Cloudy, 

24 

7 

0 

48 

58,5 

30,22 


NWbyW 

I 

Fair. 


2 

0 

58 

59,5 

30.25 


WNW 

I 

Fine. 

t 

%5 

7 

0 

49 

5^5 

30,24 


wsw 

I 

Fine. 


2 

0 

61 

60,5 

30,24 


wsw 

I 

Fine. 

26 

7 

0 

52 

59 ’S 

30,22 


w 

r 

Cloudy. 


2 

0 

63 

61, s 

30,22 


wsw 

1 

Cloudy* . 

, 27 

7 

0 

5 ° 

59>5 

30,08 


wsw 

1 

Fine. 


2 

0 

64 

6 1>5 

30,00 


wsw 

1 

Fine,, 

28 

7 

0 

5 ° 

59>5 

30,00 

°.°75 

wsw 

x 

Fine. 


2 

0 

60 

6l 

29.95 


wsw 

1 

Cloudy* 

29 

7 

0 

58 

60 

29,69 


sw 

2 

Cloudy. 


2 

0 

61 

61 , 5 

29.63 


sw 

2 

Cloudy. 

3° 

7 

0 

46 

59 

29,68 

°>353 

wsw 

2 

Fine. 


2 

0 

54. s 

59 ’SJ 

29,72 


wsw 

2 

Cloudy. 


c 2 


METE 


C ao 3 


METEOROLOGICAL JOURNAL 

for October 1789. 


1789 

rime. 

Therm. r 
without 

Therm.l 

within. 

Barom. 

Rain. 

Winds. 

Weather. 

el m. 

0 

0 

inches. . 

inch. 

Points. 

3tr. 

H-t 

0 

7 

0 

5 ° 

59 

29,20 ( 

=>,485 

SW 

2 

Cloudy. - , 1 ' 


2 

0 

52 

59 

29^9 


WSW 

2 

Cloudy. 

2 

7 

0 

46 

57.5 

29,26 

^33 

vv 

2 

Fine. j 


2 

0 

5‘,5 

59 

29,16 


w 

2 

Fair. j 

3 

7 

0 

46 

57 

29,05 

0,063 

w 

2 

Fair. i 


2 

0 

55 

58 

29^5 


w 

2 

Fair. j 

4 

7 

0 

43 

55 

29.45 


WNW 

1 

Cloudy. j 


2 

0 

5 ° 

56 

29.53 


WNW 

1 

Fair. 1 

5 

7 

0 

46 

53 

29.35 

0,020 

SW 

1 

Cloudy. ■ 


2 

0 

48, s 

53.5 

29,14 


ssw 

2 

Cloudy. ] 

6 

7 

0 

42 

53 

29,00 

0,275 

w 

2 

Cloudy. 


2 

0 

54 

58 

29,05 


WSW 

2 

Fair. 

7 

7 

0 

45 

55 

29,27 

0,053 

w 

2 

Fine. " 


2 

0 

53 

58 

29.32 


w 

2 

Fair. 

8 

7 

> 

0 

48 

55 

29,20 

0,204 

s 

I 

Rain. 


2 

0 

5 ° 

57 

29 ,H 


s 

I 

Rain. jj 

9 

7 

0 

45 

56 

29,29 

0,762 



Cloudy. 


2 

0 

5^5 

58,5 

29.35 


SW 

I 

Fair. ? 

10 

7 

0 

45,5 

56.5 

29 ; 4 ^> 


SSE 

I 

Fine. i 


2 

0 

53 

59 

29,52 


S bv W 

I 

Fair. 

11 

7 

0 

45 

57 

29.83 


S by W 

I 

Fine. :j 


2 

0 

53>5 

58 

29.79 


S by W 

I 

Fair. 

12 

7 

0 

49.S 

56,5 

29,48 

0,635 

W 

I 

Rain. j 


2 

0 

54 

58 

29,55 


SW 

I 

Fair. , 

. *3 

7 

c 

46 

57 

29, 5 2 


SSE 

I 

Cloudy. 


2 

c 

55 

58,5 

29,40 


SSE 

2 

Cloudy. 

14 

7 

" c 

46,5 

56.5 

29,38 


SE 

I 

Foggy. 


2 

c 

52,5 

5^>5 

29,42 


ESE 

I 

Cloudy. 

*5 

7 

c 

> 47 

57 

29.33 

0.39 1 

ESE 

( I 

Cloudy. 


1 2 

£ 

> 5 Z 

57,5 

29,42 


WNW 

I 

Cloudy. 


7 

C 

) 42 

56 

29,67 


WNW 

I 

Fine. 


1 2 

c 

53 

59 

29,77 


WNW 

1 

Fine. 


mete- 


[ *< ] 





ETEORQLOGICAL J 

for October 1 789. 

0 u 

R N A L 


Time. 

[Therm. 

[Therm. 

jBarom. 

j Ram. 

Winds, 





without 

[within,. 


1 

g 




T *7 3 q 






j 



Weather. 

1 / °9 






j' 




H. 

M. 

0 

0 

Inches. 

Inch. 

Points. 

Str. 


061 . 17 

7 

0 

43 

5 6 

29,92 


WNW 

1 

Fair. 


2 

0 

5 2 >5 

59 

29,90 


SW 

1 

jCloudy. 

18 

7 

0 

5 ° 

57 

29,66 


SSE 

1 

jCloudy. 


2 

0 

55 

59 

29,68 


ssw 

I 

Cloudy. 

19 

7 

0 

43 

56,5 

29,78 

0 

01 

0 

O 

s 

l 

Foggy. j 


2 

0 

55 

5 8 »S 

29,74 


ssw 

2 

Cloudy. 

20 

7 

0 

57 

58 

2 9>79 

0*072 

SW 

2 

Cloudy. 


2 

0 

59 

62 

29,87 


SW 

2 

Fine. 

21 

7 

0 


58,3 

29,90 


ssw 

I 

Fine. j 

| 

2 

0 

59 

6 3 

29,83 


SW 

I 

Fine. I 

22 

7 

0 

5 1 

58 

3 °> 01 


WNW 

I 

Cloudy. 


2 

0 

53 

60 

3°>°4 


N 

I 

Cloudy. 

2 3 

7 

0 

5 1 

5 8 

30,07 


-NE 

I 

Cloudy. 


2 

0 

57,5 

61,5 

30,08 


ENE 

I 

Cloudy. 

24 

7 

0 

5 ° 

60 

30,20 


ENE 

I 

Cloudy. 


2 

0 

53 

61,5 

3 C ),24 


ENE 

I 

Cloudy. 

25 

7 

0 

47 

58,5 

30,26 


NE 

I 

Cloudy. 


2 

0 

5 * 

59 

30,24 


ENE 

I 

Cloudy. 

26 

7 

0 

47 

57 

30,24 


N 

I 

Cloudy. | 


2 

0 

52 

59 

30,22 


NE 

I 

Cloudy. 

27 

7 

0 

44 

57 

3°> 2 5 


NW 

I 

Cloudy. 


2 

0 

46 

58 

3 °, 2 9 


NNW 

I 

Cloudy. 

28 

7 

0 

43>5 

37-5 

30,25 


SW 

I 

Foggy. ] 


2 

0 

50 

S 8 

30,22 


w 

I 

Cloudy, 

29 

7 

0 

44 

57 

3°* I 2 


WNW 

I 

Cloudy, 


2 

0 

49 

58 

3 °) 10 


w 

I 

Fair. 

3 ° 

7 

0 

40 

55 

3°’°3 


W 

I 

Fair. 


2 

0 

45 

5 f) 

29,8; 


w 

I 

Cloudy. 

3i 

7 

0 

36 

53-5 

29,87 

0 

l-l 

A 

0 

NNE 

2 

Fair* 


2 

0 

39 

54)5 

30, 1 1 1 


NNE 

2 

Fine. 


METE 


[ 2 2 ] 


METEOROLOGICAL JOURNAL 

for November 1789. 


1789 

rime. 

\ 

Therm. r 
without 1 

Therm. 1 
within. 

Sarom. 

Rain. 

Winds. 

Weather. 

S. M, 

0 

o 1 

inches. 

inch. 

Points. S 

>tr. 

Nov. 1 

2 

3 

4 

5 

6 

“ 7 

8 

9 

10 

1 1 

12 

*3 

1 <; 
it 

7 0 

2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 0 
2 0 

7 c 
2 c 

7 c 
2 c 

7 c 
2 c 
) 7 c 
1 2 c 

34 

41 

44 

48 

35>5 

46 

44>5 

47 

44 
47 

3 6 
41 

37 

41 

39 

45 
37 
44 ? 5 

3 1 ?5 

40 

34 
44 
. 42 

44 
33 

49 

42 

55 

45 

> 5 1 

) 41 

> 48 

5 2 

54 

5 2 

53>5 

5 2 
54 
5 2 >5 

54.5 
5 2 >5 
54 
5 2 ’5 

53 
5 2 

5 2 

5 1 

53 
5 I >5 

54 
5 ° 
53 

50 .5 
53 

5 2 , 
53’5 

5 2 
53’5 

52.5 
5 6 

5 3 

55 
53 

5 6 

3 °> 3 ° 

3 °, 3 ° 
29,60 

29.43 

29,18 

29,08 

29,00 

29,10 

29,25 

29,25 

28.81 

28,74 

28.72 

28,77 

29,07 

29. ! S 
29,47 
29,57 

29,76 

29.81 

29,93 

29>93 

29,65 

29.64 

29.72 
29, 5 6 

29.65 

29.41 

29.42 
29,30 

29 . 44 
29,46 

0,010 

0,100 

0,082 

0,180 

0,112 

0,1 IC 

0,03c 

0,075 

0,19c 

NW 

NW 

sw 

sw 

SW by S 
S by W 
S by W 
SSE 
SSE 
N 
N 
N 
NW 
NNW 
NW 
W 

w 
w 
• W 
w 
w 

SW by W 

wsw 

wsw 

sw 

> sw 
sw 

5 SW 

sw 

> sw 
sw 

1 

1 

£ 

2 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

1 

2 

1 

2 
I 
I 

?ine. j, 

riazy. j 

Cloudy. 

Cloudy, j 

Foggy. j 

Cloudy. 1 

Cloudy, | 

Pair. j 

Cloudy. j 

Cloudy. j 

Cloudy. 

Cloudy. I 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. : 

Fine. } 

Fair. ; 

Fine. 

Fine. : 

Fine. | 

Fine. 

Cloudy. 

Cloudy. I 

Cloudy. ' 

Cloudy. 

Cloudy. 

Cloudy. 

Rain. j 

Cloudy. 

Fair. , 

Fair. ! 


> . 


mete 


C *3 ] 


METEOROLOGICAL JOURNAL 

for November 1789, 


1789 

Time. 

iTherm. 

without 

Therm. 

within. 

Barom. 

Rain. 

Winds. 

Weather. 

H. 

M. 

0 

0 

Inches. 

Inch. 

Points. 

Str. 

Nov. 17 

7 

O 

43 

53.5 

29?45 

0,020 

SSW 

1 

Fair. 


O 

O 

46 

55.5 

29-43 


SSW 

1 

Cloudy* 

18 

7 

O 

37 

53 

29.5. 

0,126 

E 

I 

Foggy. 


2 

0 

44>5 

54,5 

29.53 


sw 

I 

Fair. 

19 

7 

0 

40 

53 

29,68 


ENE 

1 

Cloudy. 


2 

0 

45 

54 

29,71 


NE 

1 

Cloudy. 

20 

7 

0 

3 6 

53 

29,64 


W 

1 

Fair. 


2 

0 

46 

54 

29,71 


w 

1 

Cloudy. 

21 

7 

0 

37 

52 

29,90 


w 

1 

Cloudy. 


2 

0 

44 

54 

29,82 


w 

1 

Cloudy. 

22 

7 

0 

42 

52 

29,87 

0,100 

NNE 

1 

Cloudy. 


2 

Q 

46 

55 

29,92 


N 

1 

Cloudy. 

23 

7 

0 

38 

52.5 

30 , 1 ! 

0,0.70 

NNE 

1 

Cloudy. 


2 

O 

44 

53.5 

30, 15 


NNE 

1 

Cloudy. 

24 

7 

0 

36 

5 2 

30,34 


N 

1 

Cloudy. 


2 

0 

40 

53 

30,27 


WNW 

1 

Cloudy. 

25 

7 

O 

3 6 

5 i 

30,20 


V/ 

1 

Cloudy. 


2 

0 

41 

53 

30,22 


W 

1 

Cloudy. 

26 

7 

0 

36 

5 i >5 

30.28 

0,036 

E 

1 

Cloudy. 


2 

0 

37 

53 

30,35 


E 

I 

Fair. 

27 

7 

0 

28,5 

50 

30,46 


W 

1 

Cloudy. 


2 

0 

40 

5 i 

30.42 


W 

1 

Fair. 

28 

7 

0 

33.5 

5 ° 

30,42 


w 

1 

Foggy. 


2 

0 

3 ^ 

50 

30,42 


w 

1 

Cloudy. 

29 

7 

0 

35 

48 

30,37 


w 

1 

Cloudy. 


2 

0 

40 

50 

30,32 


E 

1 

Cloudy. 

30 

7 

0 

37.5 

48,5 

30,08 


S 

1 

Cloudy. 


2 

0 

38 

5 ° 

29,96 


E I 

1 

Fair. 


M E T E“ 


[ 24 3 


meteorological journal 1 

for December 1789. 

v \ 

1 

,'ime. p 
w 

?herm. 1 
/itllout v 

FhermJB 

/ithin. 

arom. 1 

lain. 

Winds. 

Weather. 

1789 - 
1 

I, M. 

o 

0 1 

nches. ll 

nch. 

Points. S 

>tr. 

Dec, 1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

1 1 
‘ 12 

I 

1 ll 

1 1 

x 

8 0 

2 0 

8 0 

2 0 

8 0 

2 0 

8 0 

2 0 
8 0 

2 0 
8 0 

2 0 
8 0 

2 0 

8 0 

2 0 

8 0 

.2 0 

8 -o 
2 0 

8 0 

2 c 
8 e 
2 c 
8 c 
2 C 
| 8 c 
2 < 

5 8 < 
2 

6 8 
2 

3 6 
44 
44 

46 

35 

37 
4 1 

47 

47.5 

5 T 

47 

5°>5 

40 

45.5 

,37 

40 

33 

33>5 

37 

42.5 

41 

> 43 

> 43 

> 46 

5 43 

) 47 

^ 37?5 

D 42 

4 45 
2 45*5 

0 34 , i 

0 28 

48 

5 1 

49’5 

53>5 

50 

5*>5 

5 1 
54 

54 

55 
54 
58 

54 

55.5 

52 

53 
545 
53 

5 1 
53 

52 

53 
- 5 2 

54.5 

53 
54?5 
52 

54 

52.5 
54 

; 50, * 

53 ,' 

29,70 

29,66 

29,60 

29,68 

29,97 

20,02 

3 °, 1 5 
3 °, 16 
30,27 
30,26 
30,38 

30,41 

3°>47 

2 °> 5 ° 

3 °> 5 ° 

30,50 

3 °> 5 6 

30,56 

3°, 54 
3°>54 
3°>53 
S°> 5 i 
3 °’ 3 ® 

30,3° 

3°>33 

30,21 

29,82 
29,71 
28,88 
28,97 
; 29,1* 

> 29, l 

0,1 1 
5 0,04 

E 

S 

S 

sw 

wsw 

w 

wsw 
sw 
sw 
wsw 
wsw 
wsw 
» w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
w 
wsw 
ssw 

E 

E 

D W 

w 

5 WNW 
WNW 

1 I 

1 I 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

2 
2 
2 
2 

: air. 

7 air. 

Cloudy. 

?air. 

Foggy. 

Foggy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

F ine. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy, 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Cloudy. 

Fine. 

Cloudy. 


— - — — - ■ 


mete 




[ ^5 ] 




— 


METEOROLOGICAL JOURNAL 

for December 1789 

1789 

Time. 

Tne 

with 

Fher 

withi 

Barom. 

Rain. 

. . . . - 

Winds. 

Weather* 

H. M. 

0 

0 

Inches. 

Inch. 

Points. 

Str., 

Dec. 17 
18 

: J 9 

20 

i 

21 

l 

1 22 

* 

23 

1 

24 

25 

26 

27 

28 

29 
3 c 
3 1 

8 0 

2 0 
8 0 

2 0 

8 0 

2 0 
8 0 

2 0 
8 0 

2 0 
8 0 
2 0 
8 0 

2 0 
8 0 

2 0 

8 0 

2 0 
8 0 

2 0 
8 0 

2 0 
8 0 

2 0 

8 c 
2 c 
; 8 c 
2 c 
8 c 
2 c 

3 

43>5 

3 6 

42 

43 
47 
40 

47 

44 

47 
5°?5 
53 

48 

5 1 
5 ° 
44 
42 

44 
33 
39 
47 
47 

45 
47 

49 

52 

45 
5 °s 5 

46 

47 

5 1 ' 

53 

5 • 

53^5 

53 

55 

5 1 » 5 1 
54? 5 | 

53 
55 

54 
57 

55 * 
57 

56 

57 .5 

55 

56 
53 
5 5 

53 

54.5 

54 

55 
54 

57 

54 
55?5 

55 

56.5 

29,10 

29,31 

20,02 

3°’°3 

29,70 

29,54 

29,70 

29.74 

29,80 

29?74 
29,54 
29,47 
29,78 
29,72 
29,24 
29,21 
29,40 
29,44 
29,78 
29,76 
29,88 
29,82 
29,87 
29 98 

29.75 

29,66 

29.76 

29,63 

29 ? 3 ° 
1 29,21 

0,165 

0,053 

0,055 

0,236 

o ,337 

0,100 

0,036 

0,053 

WNW 

WNW 

WNW 

wsw 

wsw 

sw 

WNW 

WNW 

wsw ■ 
sw 
sw 
sw 
sw 
ssw 
s 

ssw 

sw 

w 

WNW 

WNW 

W 

sw 

w 

WNW 
. sw 
ssw 
sw 
ssw 

SSE 
S by E 

2 

2 

I 

1 

2 
2 
2 
I 
I 

1 

2 
2 
2 

2 ! 

2 

iy 

■‘i 

2 

2 

1 

2 
2 
2 
2 
2 
2 

1 

2 
2 
2 

Cloudy. 

Cloudy. 

Fine. 

Fine. 

Cloudy® 

Cloudy* I 

Cloudy. | 

Cloudy. 

Cloudy. 1 

Cloudy. I 

Cloudy. , 1 

Cloudy. 

Cloudy. 

Cloudy. 

Rain. 

Rain. 

Rain. 

Cloudy. 

Fine. 

Fine. 

Cloudy® 

Rain. 

Fine. 

Fine. 

Rain. 

Cloudy. 

Cloud]?^ 

Cloudy. 

Cloudy, 

(Cloudy. 


d 


Vo l. LXXX. 


M E T El 


/ 


E I 



Thermometer 

without. 

Thermometer 

within. 

Barometer. 


w 

*<r 

oo 

SO 

1 

Greateft 

height. 

■a z 

S M 

-4 ’5 

C~] 

Mean 
height. 1 

Greateft 

height. 

Dealt 

height. 

Mean 

height. 

Greateft 

height. 

Leaft 

height. 

Mean 

height. 

Rain. 

January 

Deg 

53 >° 

Deg. 

' 7.5 

Deg. 

35’7 

Deg. 

36 

Deg. 

3 6 

Deg. 

46 

Inches. 

3°»75 

nches. 

28,58 

nches. 

29,72 

Inch e 
',345 

February 

51, ° 

34 

42.5 

57 

49 

52,5 

3°>34 

28,65 

29 , 7 ° 

1,605 

March 

4^)5 

26 

36,6 

52 

44 

478 

3 <V 3 

28,94 

29,72 

i,S 49 

jApril 

62 

29 

47 > 2 

61 

48 

54.2 

3 °. 18 

29,1° 

29>77 

0 ,957 

|May 

66 

45 

5 6 )9 

65.5 

55 

60,5 

3°.27 

29,57 

29,88 

1,103 

jjune , 

72 

50 

5 8 >5 

66 

5^*5 

61,5 

3°> 2 3 

29,40 

29,84 

3> 2 44 

p>y 

71 

52 

61,9 

65 

59 

63.5 

30,09 

29,54 

29,85 

2,467 

Auguft 

74.5 

54 

63.7 

69 

62 

66,2 

3°, 33 

29,70 

30,06 

1,864 

September 

1 

74 

45 

57>3 

68 

58,5 

62,6 

3 °. 3 8 

29,3° 

29,88 

2,155 

October 

59 

3 6 

49> x 

63 

53 

57.5 

3°? 2 9 

29,00 

29,52 

3> 2 53 

November 

55 

28,5 

41,0 

56 

48 

52,6 

30,46 

28,72 

29,70 

1,244 

December 

53 

33 

43.5 

58 

48 

53 . 6 

30,56 

28,88 

29,86 

1,19° 

jWhole year 

- 1 1 — 


49 ’5 



56.5 

1 

29,79 

21,976 


end of FART I. 


I 


OF VOL. LXXX. 


PHILOSOPHICAL 

TRANSACTIONS, 

OF THE 

ROYAL SOCIETY 

O F 

L O N D O N. 

s. 


VOL. LXXX. For the Year 1790. 
PART II. 



fc . 

- LONDON, 

BOLD BY LOCKYER DAVIS, AND PETER ELMSLY* 
PRINTERS TO THE ROYAL SOCIETY. 


MDCCXCI. 





c o 





mr\ 


s 


O F 


VOL. LXXX. Part 


rom 


XIII. Account of the Tabajheer . In a Letter ft 
Patrick Ruflell, M. D. F. R. S. to Sir Jofeph 

BcinkS} Li a it' P. R . S. p^gg 2 y yy 

XIV. Account of the Nardus Indica , or Spikenard. By Gilbert 

Blane, M. D. F. R. S. p. 284 

XV. An Account of fome extraordinary EffeSis of Lightning-. 

By William Withering, M. D. F. R. S. p. 29 . 

XVI. An Account of a Child with a double Head. In a Letter 
from Everard Home, Efq. F. R. S. to John Hunter, E/a. 

T? T> C 

± * 1X9 p. 296 

XVII On the Analyfs of a Mineral Subfance from New South- 

Wales. In a Letter from jofiah Wedgwood, Efq. F. R S. 
and A. S. to Sir Jofeph Banks, Bart . P. R. 5 . p. 306 

XVIII. Report on the befi Method of proportioning the Excife 
upon Spirituous Liquors . By Charles Blagden, M. D. Sec . 


R. S. and F . A. S. 


p. 3 2I 


XIX Obfervations on the Sugar Ants . In a Letter from John 
Ca files, Efq. to Lieut. Gen » Melvill, P* R . S. p, ^46 

XX. Experiments and Obfervations on the Diffolution of Metals 
in Acids 9 and their Precipitations ; with an Account of a new 
compound acid Menfruum , ufeful m Jome technical Operations 
of parting Metals. By James Keir, Efq. F , R. S> p. 359 

N n z “ XXL 


IV 


CONTENTS 


XXL Determination of the Longitudes and Latitudes of fotnt 
remarkable Places near the Severn. In a Letter from Edward 
Pigott, E fa. to Sir Henry C. Englefield, Bart. F. R. S. p. 335 
XXII. Experiments and Obfervations on the Matter of Lancer 
and on the aerial Fluids extricated from animal Sub/lances by 
Diftillation and Putrefaction ; together -with fame K f m f r f ™ 
fulphureous hepatic Jir. By Adair Crawford, M. D. t.K. i. 

XXIII. On the Satellites of the Planet . Saturn, and the Rotation 
of its Ring on an Axis. By William Herlcnel, L L.D. 

F. R . S. • 

XXIV. On Spherical Motion. By the Rev. Charles Wildbore ; 

communicated by Earl Stanhope, F. R . S. 

XXV. On the Chronology of the Hindoos. By VV llham Madden, 

Efq. F. R. S. and A. S. P- 5 b0 


A P 


E N D I X. 


Remarks on Major-General Roy’s Account of the ^“e 
meal Operation, from Page ill. to Page 270. of this Volume ’ 
By Mr. Ifaac Dalby. P' 


ERRATA. 

PART I. 

t. 229. laft column of the Table, and lafU'me but one of that column, fir 

V. 250. Triangfe XIII. diftance of Norwood from Chiflehurft Church in feet, 
for 35777-9 read 36777-9- 

part II. 

P. 346. 1 . 3. for May 22. read May 20 . 

P. 370. 1 . 23. fir by read without. 


PHI- 


4 J*309JR 4***4 . <* |®> 4***4 ?***[ 


^ ^ c 2§ - 

hMMM *% 






# M 

VOOOSLmE 




PHILOSOPHICAL 


TRANS ACTIONS. 


XIII. <^/z Account of the Tabajheer . In a Letter from Patrick 
Ruffell, .M, D. F. F. /S’. /a SVr Jofeph Banks, Bart* 

P* R. S. 

i(, . ■' ' \ "’ ’ ;v ' >'’• '"'■/’ : - t ' .’ '*''" ■ • ■ '*•>- • " ' ’ ■ .- T A / " . 

, 3 f m ■ >. (. ; ";■' . ’ ■ ■ , . , . 

Read March ii, 1790* 

SIR, 

S HOULD the following remarks on the Tabaflieer, a medi- 
cine in high repute in many parts of the Eaft, appear 
defending a place in the Tranfadions, you will do me the 
honour to prefent them, together with the accompanying fpe- 
mens, to the Society. ■- . v 

This di*ug was, I believe, firfl introduced to the knowledge v 
of the weftern world through the works of the Arabian phy- 
Vol. LXXX. O o ficians, 

1 


/ 




Dr. RussEll’j Account 

ficians all of whom mention it as an important article in their 
Materia Medica; and, from what 1 could obferve in Syria, it 
ftill continues to be in much more general ufe in Turkey than 

in this part of India. 

To the Arabs and Turks it is known under the name of 
Tabafheer only ; at lead I never heard any other name given 
to it in Syria, nor even at Conftantinople ; under that name 

alfo it is mentioned by the Arabian writers. 

In this country, befides that of Tabafheer, which they had 
from the Perfians, it is known under feveral other names. 

Tn the Gentoo language it is called Vedroo-paloo, am oo- 
milk ; in the Malabar, Mungel Upoo , Salt of Bamboo ; and in 
the Warriar, Vedroo Carpooram, Bamboo Camphoi. 

Don Garzia dall’ Horto has long ago expofed a dangerous 
error, common to the old tranflators of the Arabian writers, 
refpeding this drug. In the Latin verfions of Rhazis and 
Avicenna, Tabafheer is conftantly rendered Spod.um; anc 
this interpretation has been adopted by mofl of the fubfequent 
tranflators of other Arabian medical writers. 

The late Mr. Channing, when engaged in the tranflation 
of Rhazis on the Small-pox, applied to me, then in Syria, 
for fuch information as I might be able to colled on the fub- 
ied of Tabafheer at Aleppo. I accordingly transmitted to him 
various fpecimens of the drug, together with feveral extrads 
relative to it, from books found in the Aleppo libraries. Some 
of thofe fpecimens differed confiderably from thofe now laid 
before the Society $ and, from what I have had occafion to ob- 
ferve during my refidence here, I am convinced, much of the 
drug commonly vended in Turkey is fiditious or adulterated. 

Having none of the Arabian medical writers at han , can 
not pretend to Arid accuracy ; but, to the belt of 

7 


of the Tabajheer. zys 

legion, they generally agree in the Tabaflieer being a pro- 
duction of the Indian reed ; more efpecially of fuch as have 
fuffered from fire, kindled by the friction of the reeds one 
again ft the other ; an accident fuppofed to happen frequently in 
the dry lea foil, among the hills, where the bamboo forms vaft 
and impenetrable thickets. 

Several of the mountaineers, with whom I have converfed 
on the fubjcct, affirm, that the bamboo is not the only tree 
fubjeft to accidental ignition by friction, and named one or 
two other trees liable to the fame accident ; but added, they 
never looked for Tabaflieer in the half- burnt fragments of the 
bamboo, though they doubted not it might fometimes be found 
there as well as in others. 

The genuine Tabaflieer is undoubtedly a production of the 
Arundo Bambos of Linnaeus, the Uy of the Hortus Mala- 
baricus, and the Arundo Indica arbor m maxima , cortice fpi- 
ttofo, of Herman. It is no lefs certain, that fire is not a ne- 
cefiary agent in its production, whether the conflagrations in 
the mountains juft now mentioned be reckoned fabulous or 
not. 

The bamboo in which the Tabaflieer is found is vulgarly 
called the Female Bamboo, and is diftinguifhed by the large- 
nefs of its cavity from the male, employed for Ipears or 
lances. They are faid to be feparate trees ; but this fa£t I 
have not had it in my power to afcertain. 

Of the feven pieces of bamboo which accompany this Pa- 
per, four are from the mountains in the vicinity of Vellore, 
and three from a place twenty miles from hence. The former 
were perfectly green on their arrival at Madras ; and the others 
were feleded from a large parcel, which were green alfo when 
they came to my hands. Thefe were all feledted on a con- 

O o 2 jedture 


2 «6 Dr. Russell’s Account 

jefture of their containing Tabafheer, from a certain rattling 
perceived upon lhaking the bamboo, as if fmall ftones were 
contained in the cavity. 

This, by the natives, is confidered as an indication of Ta- 
bafheer being contained in one or more joints of the bamboo, 
and they are feldom difappointed ; but it does not always fol- 
low, that there is no Tabafheer where a rattling is not per- 
ceptible ; for, upon fplitting a number of reeds, it was fome- 
times remarked, that where the quantity of the drug was in- 
cotifiderable, it was found adhering fo clofely to the fides of the 
cavity, as to prevent any rattling fiom being pciceivcd upon 
fhaking. In general, however, the rule of the natives for 
choofmg the bamboos proved a good one. 

In the month of April, one of the bamboos, confiding of 
fix joints, received from Vellore, being cautioufly fp lit, each 
joint was examined feparately. In two ot them no vefhge of 
the drug was difcovered ; each of the others contained fome, 
but in various quantity j the whole colle&ed amounted to about 
twenty-feven grains. 

The quality alfo was various. The particles reckoned of the 
firft quality were of a bluifh white colour, refembling fmall 
fragments of fhells ; they were harder than the others, but 
might eafily be crumbled between the fingers into a gritty pow- 
der, and when applied to the tongue and palate had a flight 
faline teftaceous tafte : they did not exceed in weight four 
grains. The reft were of a cineritious colour, rough on the 
furface, and more friable ; and intermixed with thefe were fome 
larger, light, fpongy particles, fomewhat refembling pumice- 
ftones. It is probable, that the Arabs, from thefe appearances 
of the drug, were led into the opinion already mentioned of 
its production. 


The 


of the Tabajheer. \ 2 yf 

The two middle joints were of a pure white colour within, 
and lined with a thin film ; it was in thefe chiefly the Ta- 
bafheer was found. The others, particularly the two upper 
joints, were difcoloured within, and in fome parts of the 
cavity was found a blackifh fubftance in grains or in powder 
adhering to the Tides, the film being there obliterated. In two 
or three of the joints, a fmall round hole was found at top and 

bottom, which feemed to have been" perforated by fome 
in fed. 


In the month of July, forty-three green bamboos, each 
confiding of five or fix joints, were brought from the hills 
fifty miles diftant from hence. Six, appearing to contain more 
Tabafheer than the others, were fet apart; the remaining 
thirty-feven were fplit and examined in the manner before- 
mentioned. The refult was as follows. 

In nine out of the thirty-feven there were no vefliges of 
Tabafheer. In twenty-eight fome were found in one, two, or 
three joints of each ; but never in more than three joints of 
the fame bamboo. The quantify varied, but in all was incon- 
fiderable ; and the empty joints were fometimes contiguous, 
fometimes interrupted, indifferently. 

The drug confifts of very diffimilar particles at firfl when 
taken rrom the bamboo, as will appear in looking into the 
fmall fpecimen, -N° i.; which, having collected myfelf, I am 
certain has undergone no adulteration. 

The whiter, fmooth, harder particles, when not loofe toge- 
ther with the others in the cavity, were moftly found adher- 
ing to the feptum that divides the joints, and to the fides con- 
tiguous ; but never to the fides about the middle of the joints ; 
and it may be remarked, that, inftead of being chiefly found at 
the lower extremity of the joint, as might be expeded from 

2 the 


© Dr. Russell’s Account 

the juice fettling there, they were found adherent indifferently 
ex, remit?, and fometimes to both. I. A- 
they formed a fmooth lining, fomewhat refembliug policed 
.ftucco, which ufually was cracked in feveral places, and mig it 

eafvly be detached with a blunt knife. 

In fome joints the Tabafheer was found thus collected at one 

or both extremities only, and in fuch no rattling was perceived 
.upon (baking the bamboo; but generally, while fome adhc 
to the extremities of the joint, other detached pieces were m- 
termixed with the coarfer loofe particle* m the cavity. 

The quantity found in each bamboo was very inconliderable , 
the produce of the whole twenty-eight reeds, from five to 
feven feet long, not much exceeding two drams. . 

It is remarked by Garzius, that the Tabartieer is not oun 
in all bamboos, nor in all the branches indifcrimmately ; bu 
only in thofe growing about Bifnagur, Batecala, and one pa 

of the Malabar Coaft. 

From the inconfiderable quantity procured from twenty- 
eiaht bamboos, it feems very probable, that, though not a o 
lately confined to certain regions, it may be produced in grea e 
abundance in fome foils than in others; but that, in all region 
where the bamboo grows favourably, fome proportion of he 

drug will be found, however it may vary in qua.ity or qu 
♦ 

“rumphius on this fubjeft refers to Garzius, candidly ac- 
knowledging, that he had not himfelf had opportumUes oj 

making particular enquiry. 1 expea anfwers from Ce 
fome queries fent thither fome time ago ; and, m refped - 

h,va b«e» Informed in a letter A. HydraM, 

from a medical gentleman attending the prefent emb.fly to t. 
Nizam, “ That thongh Tabalheer be in great requeft «JHy- 


u 

it 

a 

a 

a 

a 

tc 

a 

<c 

66 


the 'Tabajheer. 279 

drabad, and bears a high price, it is never brought thither 
from Bifnagur ; that fome of what is found in the Bazars is 
brought from the Atcour pafs in Canoul, and fome from 
Emnabad at the diftance of about eighty miles to the N.W. ; 
but that the greateft part comes from Mafulipatam. 

“ That there are two forts fold in the Bazars ; one at the 
rate of a rupee a dram; the other, of inferior quality, at 
half the price ; but that this is faid to be chiefly compofed 
of burnt teeth and bones. 

“ That he was informed by a Perfee, who had been in 
Bengal, that the Tabafheer was produced in great quantities 
at Sylhet, where it fold by the pound from one rupee to one 



“ and a half, and formed a confiderable article of trade from. 
“ Bengal to Perfia and Arabia.” 

N° 3. is a fpecimen of the prime fort from Hydrabad. It 
differs materially from the others, not only in its fuperior 
whitenefs, and the being lefs mixed with impure particles; 
but in the being much harder than the pureft particles of my 

fpecimens, much heavier, and hardly in any degree friable to 
the finger. 

Submitting the fpecimens to examination, I refrain from 
experiments on them which may more fuccefsfully be made in 
England, and (hall proceed to offer a few obfervations on the 
juice of the recent bamboo fuppofed to form the Tabafheer. 

Rumphius remarks in Amboina, “ Juniores arundines ple- 
“ rumque in inferioribus fuis nodis femi-repletae utcunque funt 
46 lympida aqua potabili, quae hifce in terris fenfim evanefcit, 
“ ' m vero regionibus exficcatur in fubftantiam albam et 
44 calceam, quae Tabaxir vocatur.” 

Garzius gives an account fomewhat different from this. I 
am obliged to cite from an Italian tranflation. “ Fra tutti 

46 gli 


„g 0 Dr. Russell’s Account 

“ gli intermezzi de’ nodi, fi genera un certo liquore dolce 
“ e grofl'o, e ridotto in guifa di farina d’ amido, e della iftefla 
“ bianchezza, et alle volte fe ne genera aflai, aile volte poco, 
“ ma non tutte le canne, ne meno tutti i rami generano tale 
“ humore Quefto liquore dopo d’ eflere apprefo, 


“ moftra d’ eflere di color nero, over cinericcio, e non percio 
it g tenuto per trifto, imperoche quefto avviene, o perche lia 
“ troppo humido, 6 perche fia flato lungo tempo nel ltgno rin- 
“ chiufo, fi come s’ hanno penfato alcuni : conciofiache in molti 
46 rami, che non fono ftati toccati dal fuoco, mti av enga quefto *• 
The exiftence of this fluid in the bamboo is known by 
{baking the joint. In a confiderable number of bamboos fplit 
in order to procure it, I never found water in more than two 
joints, and generally not more than two or three drams in 
each ; the largeft quantity procured at one time was one ounce 
and a half. Very few joints in proportion contained any. 

The fluid was always tranfparent, but varied in conliftence ; 
when thicker it had a whiter colour than common ; when 
more dilute it differed little to the eye from common water, or 
fometimes had a pale greenilh caft. Applied to the tongue and 
palate, it had a flight faline, fub-aftringent tafte, more or lefs 
perceptible in proportion to the conftftence of the fluid. After 
evaporation in the fun, the refiduum had a pretty ftrong faline 
tafte, with lefs aftringency. Some of the fluid, of a darkifti 
colour, thickened in the reed to the conftftence of honey; and 
fome, in another joint of the fame reed, was perfectly white and 
almoft dry : both had the fharp fait tafte, which theTabalheer 
itfelf lofes in a great degree by keeping. 

From two green bamboos, each of five joints, which had 
been cut only a few days before, I procured above two ounces 


* Capitolo XII 8 


of 


of the \ Tabq/heer . 281 

of fluid ; it had a flight Mfie tafte, and in colour had a 
greenifh caft. • ' 

One ounce was put into a phial, N° 1 . and about ten drams 
into another phial, N° 2.; both were flopped with glafs flop- 
pers. After two days they had both depofited a fmall fedi- 
ment; but the fediment in N° 1. was three times more than 
that in the otner. At the end of the week, the water in 
both was found fweet, and the fediment increafed, but moft 
in N° 1. 

At the end of fortnight, the water in N° 1. had a fetid 
fmell, with a whitifh cottony fediment, and a thin film of 
the fame kind fufpended at top. The whole, well fliaken 
together, was poured into a glafs veflel, and left to evaporate 
flowly. The refiduum confifted of fmall particles of a whitifli 
brown colour, refembling the inferior fort of Tabaflieer. 

The water in N° 2. had hardly any fetid fmell at this time ; 

and at the end of the month remained in the fame ftate: the 

fediment had increafed verv little. 

«/ 

The recent green bamboos, which, upon fhaking, appeared 
to contain water in the cavity, loft this appearance after (land- 
ing a few' days, feme fooner, fome later. When fplit, after 
they no longer gave any found by fliaking, fometimes no fluid 
was found in the cavity, as if the whole had efcaped. The 
interior thin pellicle, however, was difcoloured,' as if by recent 
moifture; but generally fome of the fluid remained in a muci- 
laginous ftate, more or lefs thick, at the lower part of the 
joint. It may be remarked, that fmall worms were fometimes 
found in the fame joints with the water, which furvived feveral 
hours, fwimming about in the water after its extraction. 

I11 the latter end of October, a green bamboo of five joints 
was brought to me, which appeared to contain both water and 
Vql. LXXX. P p Tabaflieer. 


2 g 2 Dr. Russell’s Account 

Tabafheer. After three days, the found of water, upon disking - 
the reed, could hardly be perceived ; oil the fifth day it was 
intirely imperceptible. 

Upon Splitting the bamboo, about half a dram of the fluid, 
now thickened into a mucilage, was found at the bottom ot 
the upper joint. The fecond joint contained fome perfed Ta- 
bafheer loofe in the cavity. The third joint was empty, ex- 
cepting a few particles of Tabalheer, which adhered to the 
fides near the bottom. The fourth joint, at the bottom, con- 
tained above a dram of a brownilh pulpy fubdance, adherent. 
The lad joint, in like manner, contained half a dram of a 
fubdance thicker and harder in confidence, and nearly of the 
colour of white wax. 

This fpecimen exhibited at one view the progrefs of the Taba- 
fheer through its feveral dages. The found didindly perceived 
in the fird joint on the 23d of Odober was produced by the 
water in a fluid date; on the gid, having become thicker, the 
found, upon fhaking, was very obfcure ; on the 2d of No- 
vember, no found was perceptible; and when the reed was 
fplit, the water was found reduced to a mucilage. The fourth 
and fifth joints contained the drug in a more advanced date. 
In the fird, it was thicker than a mucilage of a brownilh 
colour ; in the fecond, more of the fluid part having evapo- 
rated, the colour was whiter, and it wanted but little of the 
confidence of the perfed Tabalheer found in the fecond joint. 

I am, &c« 

"1 

FAT. RUSSELL. 

Vizagapatam, 

Nov. 26, 1788, 

\ 

POST" 


of the Tabajheer . 


283 

POSTSCRIPT. 

Weymouth Street, July 16, 1790.. 

FOUR of the feven reeds prefented to the Society on the 
night this Paper was read, being carefully fplit, the contents, 
upon comparing them with the fpecimens fent from India, 
then on the table, were found to agree in all refpe£ts, as well 
as with the defcription of the more recent drug given in the 
above Paper. The fpecimen, N° 3. fent from Hydrabad, and 
reckoned the prime fort, differed fomewhat in hardnefs, as 
mentioned above, from the pureft particles in the Tabafheer 
collected by myfelf; but in the opinion of feveral of the 
Members prefent, who compared them, were the fame 
fubftance with the particles mixed, in a fmall proportion, 
in fome of the other fpecimens, as likewife with a few par- 
ticles taken from the reeds opened in their prefence ; which 
puts it beyond doubt, that the fubftance is produced in the 
cavity of the Bamboo. 

V 

The feveral fpecimens are now under chemical trial ; and 
the refult of the experiments will, I hope, be communicated 
to the Society. 




P p 2 


[ 28 4 J 


XIV. decount of the Nardus Indica , or Spikenard . 
By Gilbert Blane, M . D. F. R . & 


Read March 18, 1790. 

I T is much to be regretted, that the records of antiquity afford 
fuch imperfeft defcriptions of natural objefts, particularly 
of thofe of the vegetable kingdom. Moft of the writings of 
the ancients have come down to us either mutilated by the 
accidents of time, or diftorted and corrupted by unfaithful and 
ignorant transcribers. There is rea'on to think, that the 
learned works upon profeffional lubjedls have been more unfor- 
tunate in thefe refpedts than works of imagination and general 
fcience, for the former are in fa£t more obfeure and confufed ; 
and as they would be lefs generally interefting, and lefs intelli- 
gible, to transcribers, they would or courfe be more liable to 
negleft and miftake. But fuppoffng the works of Theo- 
phrastus, Dioscorides, and the other ancient phyficians 
and naturalifts, to be extant in tneir utmoft completenefs and 
purity ; their method ot describing plants and other natural 
bodies was fo defective, that very few of them could now be 
recognized. We have not only to contend with the G~fcurity 
belonging to a dead language, in fo far as the name merely is 
concerned; but it would be impoffible, even in a living lan- 
guage, to perpetuate the knowledge of any obje£t in nature, 
fuch as a plant, without fome defeription to diferiminate it 

from 


1 


Dr. Blank's Account , &c. 2% 

from all others. For want of fuch defcriptions, the know- 
ledge contained in the writings of the ancient naturalifts could 
be of ule only to their contemporaries and countrymen, who 
were already acquainted with the objects of it, and could 
afford no certain information to the ignorant in diftant coun- 
tries and future ages. Of all the ancient medicines, there 
is perhaps none but opium, of which the identity can be un- 
queftionably afcertained. Of mod: of them little more is faid 
than merely giving their names. But while nature is. conftant 
and invariable, language is local and fluctuating, fo that- feme 
of the mo ft important knowledge, though committed to wri- 
ting, refts upon little better foundation than if it were vague 
tradition. In confequence of this ambiguity, the fruits of the 
ingenuity and labour of one age have, in a great meafure, been 
loft to another; and ufeful inventions in various arts have be- 
come extiinft, for want of the means of afeertaining the ma- 
terials employed in them. Pofterity will therefore be greatly 
indebted to thofe induftrious naturalifts of the prefen t times 
w ho are carrying the defeription of nature to an unexampled 
height of improvement ; and our lateft defendants will be 
enabled, without difficulty, to avail themfelves of the accu- 
mulated experience of preceding ages. 

I have been led to thefe reflexions by an account, fen t me 
fome time ago by my brother in India, of the Spikenard, or 
Nardus Indica , a name familiar in the works of the ancient 
phyfieians, naturalifts, and poets ; but the identity of which 
has not hitherto been fatisfadtonly afeertained. Fie lays, in a 
letter dated Lucknow, December iy86, that, * 6 travelling 
with the Nabob Vifier, upon one of his hunting excurlions 
towards the northern mountains, I was furpnfed one day, 
u after croffing the river Rapty, about twenty miles from the 

“ foot: 


Dr. Blane’s Account of 

«' foot of the hills, to perceive the air perfumed with an aro- 
m atic fmell; and, upon aiking the caufe, I was told it pro- 
« ceeded from the roots of the grafs that were bruifed or 
“ trodden out of the ground by the feet of the elephants and 
“ horfes of the Nabob’s retinue. The country was wild and 
“ uncultivated, and this was the common grafs which covered 
tt t he furface of it, growing in large tufts clofe to each other, 

“ very rank, and in general from three to four feet in length. 

“ As it was the winter feafon, there was none of it in flower. 

“ Indeed, the greateft part of it had been burnt down on the 
“ road we went, in order that it might be no impediment to 
^ the Nabob’s encampments* 

“ I collected a quantity of the roots to be dried for ufe, and 
« carefully dug up fome of it, which I fent to be planted in my 
“ garden at Lucknow. It there throve exceedingly, and in 
“ the rainy feafon it fhot up fpikes about fix feet high. Ac- 
« companying this, I fend you a drawing of the plant in flower, 
“ and of the dried roots, in which the natural appearance is 

“ tolerably preferved. 

“ It is called by the natives Terankus, which means literally, 
« i n the Hindoo language, fever-reftrainer, from the virtues 
« they attribute to it in that difeafe. They infufe about a 
“ dram of it in half a pint of hot water, with a fmall quan- 
<. tity of black pepper. This infufion ferves for one dofe, and 
« is repeated three times a day. It is efteemed a powerful 
« medicine in all kinds of fevers, whether continued or inter- 
« mittent. I have not made any trial of it myfelf; but ihall 
«( certainly take the fir ft opportunity of doing fo. 

“ The whole plant has a ftrong aromatic odour; but ot 

U the fmell and the virtues refide principally in the hulky 

« roots, which in chewing have a bitter, warm, pungent tafte, 

“ accom- 


2 


the Nardus Indica, or Spikenard. 2 g 

“ accom P an ied with fome degree of that kind of glow in the 
** mouth which cardamoms occafion.” 

Befides the drawing, a dried fpecimen has been fent, which 
was in fuch good prefervation as to enable Sir Joseph Banks, 
P. R. S. to a fcer tain it by the botanical characters to be a fpe- 
cies ot ' ^ndropagon, different from any plant that has ufually 
been imported under the name of Nardus, and different from 
any of that genus hitherto deferibed in botanical fyftems. 

There is great reafon, however, to think, that it is the true 
Nardus Indica of the ancients ; for, firft, the circumftance, in 
the account above recited, of its being difeovered in an unfre- 
quented country from the odour it exhaled by being trod upon 
by the elephants and horfes, correfponds, in a ftriking man- 
ner, with an occurrence related by Arrian, in his Hiftory 
of the Expedition of Alexander the Great into India. It is 
there mentioned, lib. VI. cap. 22. that, during his march 
through the defarts of Gadrofia, the air was perfumed by the 
Spikenard, which was trampled under foot by the army } and 
that the Phoenicians, who accompanied the expedition, col- 
leded large quantities of it, as well as of myrrh, in order to 
carry them to their own country, as articles “of merchandife. 
This I aft circumftance feems further to afeertain it to have 
been the true Nardus ; for the Phoenicians, who, even in war 
appear to have retained their genius for commerce, could no 
doubt diftinguifh the proper quality of this commodity. I am 
informed by Major Rennell, F. R. S. whofe accurate re- 
learches in Indian geography are fo well known to the publick 
that Gadrofia or Gedrofia anfwers to the modern Mackran or 
Kedge-Mackran, a maritime province of Perfia, fituated be- 
tween Kerman (the ancient Carmania) and the river Indus 
being of courfe the frontier of Perfia towards India; and that 


It 


sg ' Dr. Blank’s Account of 

it appears from Arrian’s account, and from a Turkifli map 
of Perlia, that. this define lies in the middle of the ttaft of 
country between the ri.er Indus and the Perhan Gulph an 
within a few days match of the Arab, an or Erythraan ft.-. 

I would appear, that the Nard was found towards the eaft.m 
of it ■ foe Alexander was then directing his route to the 
leftward,' and the length of march thiou S h ‘he deftrt after- 
i c was verv great, as they were obliged to kill their beat 
: Ltdlnln lnfecuen'ce of tlfeir fuhfegnen, diftrefs Second y - 
though the accounts of the ancients concerning this plant are 
obfeure and defeftive, it is evident, it was a plan o 
order of grmi m ; for the term nri/b, lh often applied to it 
li appropriated by them to the fruftification of grants and 
orafles and feems to be a word of Greek original to denote 
ihe Jft excellent portion of theft plants, which are toe nroft 
ff-1 in the vegetable creation for the fuftenance of animal 
Ufe and nature has alio kindly made them the moft abundant 
111 n^rts of the habitable earth. The term faca is applied to 
phots' of the natural order verticillat*, m which there are 
toy fpecies of fragrant plants, and the lavender, which being 
,u indigenous one, affording a grateful perfume, was called 
NardJltalica by the Romans; but we never hnd the ter 
■a r.pd to thefe The poets, as well as the naturalifts, 

conftautly apply this latter term to the true IN ardus. Stati 

“Ss Ac Spikenard odarata anjia. Ovid, m men Honing * 
"tie of the materials of the Phoenix’s neft, calls it 
kvis arijh ; and a poem, afenbed to Lactantius, on 

. By the Erythraean Sea the ancients meant the northern part of the 
' . . r coa fts of Arabia and Perfia, and not, as tne 

OC T;’ W twh«U intern times, called the Red Sea. The ancient name 
would imply, what is, m 

of the Red Sea was Sinus Arabicus. fame 


the Nardus Indica , or Spikenard* 289 

fame fubjeft, fays, his addit teneras Nardi pubentis ariftas, 
where the epithet pubentis fee ms even to point out that it be- 
longed to the genus andropogon , a name given to it by Lin« 
njevs from this circumftance. Galen fays, that though 
there are vanous forts of Nardus , the term or 

Spikenard, ffiould not be applied to any but the Nardus Indica. 
It would appear, that the Nardus Celtica was a plant of a quite 
different habit, and is^ fuppofed to be a fpecies of Valeriana . 
The defcription of the Nardus Indica by Pliny does not in- 
deed correfpond with the appearance of our fpecimen ; for he 
fays it is frutex radice pingui et crajjd ; whereas ours has fmail 
fibrous roots. But as Italy is very remote from the native 
country of this plant, it is reafonable to fuppofe, that others, 
more ealiiy procurable, ufed to be fubftituted for it ; and the 
fame author fays, that there were nine different plants by 
which it could be imitated and adulterated. There would be 
ftrong temptations to do this from the great demand for it, and 
the expence and difficulty of diftant inland carriage ; and as it 
was much ufed as a perfume, being brought into Greece and 
Italy in the form of an unguent manufactured in Laodicea, 
Tarfus, and other towns of Syria and Afia Minor, it is proba- 
ble, that any grateful aromatic refembling it was allowed to 
pafs for it. It is probable, that the Nardus of Pliny, and 
great part of what is now imported from the Levant, and 
found under that name in the (hops, is a plant growing in the 
countries on the Euphrates, or in Syria, where the great em- 
poriums of the eaftern and weftern commerce were fituated. 
There is a Nardus Ajfyria mentioned by Horace; and Dios- 
corides mentions the Nardus Syriaca , as a fpecies different 
from the Indica , which certainly was brought from fome of 
the remote parts of India ; for both Dioscorides and Galen, 
Vol. LXXX. Q^q by 


/ 


Dr. Blane’s Account of 

by way of fixing more precifely the country from whence It 
comes, call it alio Nardus Gangites. Thirdly, Garcias ab 
Horto, a Portuguefe, who refided many years at Goa in the 
lixteenth century, has given a figure of the roots, or rather the 
lower parts of the ftalks, which correlponds with our fpeci- 
men ; and he lays expreflly, that there is but this one fpecies 
of Nardus known in India, either for the confumption o. 
the natives, or for exportation to Perfia and Arabia. It is. 
remarkable, that he is perhaps the only author who fpeaks of 
it in its recent ftate from his own obfervation. It is not to be 
met with among the many hundreds of plants delineated in 
the Hortus Malabaricus. The Schcenanthus of Rumphius 
does not correfpond with it, being only one palm in height , 
but he mentions having feen a dried fpecimen of it, of which 
the leaves were almoft five feet high ; and that Mackran was 
one of the countries from whence it was brought. This mull 
be the fame as that mentioned by Arrian, but differs fiom 
that of Garcias in the length of the ftalks; but this might 
be either becaufe the meafure was taken at dirierent feafom of 
the year, for the fpecimen before us was much fhorter -in 
winter than when it fhot into fpikes, or uecauie that o. Gar 
ci as being, according to his own account, cultivated, it 
might not be fo luxuriant as that which grew fpontaneous in its 
native foil. Fourthly, the fenfible qualities of this are fupe- 
rior to what commonly palfes for it in the fhops, being pof 
feffed both of more fragrancy and pungency, which feems to 
account for the preference given to it by the ancients. 

There is a queftion concerning which Mathiolus, the 
commentator of Dioscorides, beftows a good deal of argu- 
ment, viz. whether the roots or ftalks were the parts efteemed 

for ufe. the teftimony of the ancients themfelves on this point 

being 


the Nardus Indie a ^ or Spikenard. 291 

being ambiguous. The roots of this fpecimen are very fmall, 
and poffefs lenfible qualities inferior to the reft of the plant ; 
yet it is mentioned in the account above recited, that the virtues 
refide principally in the bujky roots. It is evident, that by the 
huiky roots mud here be meant the lower parts of the ftalks 
and leaves where they unite to the roots ; and it is probably a 
flight inaccuracy of this kind that has given occafion to the 
ambiguity that occurs in the ancient accounts. 

With regard to the virtues of this plant, it was highly valued 
anciently as an article of luxury as well as a medicine. The 
favourite perfume which was ufed at the ancient baths and 
feafts was the Unguentum nardinum ; and it appears, from a 
paflage in Horace, that it was fo valuable, that as much of it 
as could be contained in a fmall box of precious ftone was con-* 
fidered as a fort of equivalent for a large veflel of wine, and a 
h and ib me quota for a gueft to contribute at an entertainment, 
according to the cuftom of antiquity : 

Nardo vinum merebere 

Nardi parvus onyx eliciet cadum . 

It may here be remarked, that as its fenfible qualities do not 
depend on a principle fo volatile as effential oil, like moft other 
aromatic vegetables, this would be a great recommendation to 
the ancients, as its virtues would thereby be more durable, and 
they were not acquainted with the method of colle&ing eflen- 
tial oils, being ignorant of the art of diftillation. The fragrance 
and aromatic warmth of the Nardus depends on a fixed principle 
like that of cardamoms, ginger, and fome other fpices. I 
tried to extract the virtues of the Nardus by boiling water, by 
maceration in wine and in proof Ipirits, but it yielded them 
but fparingly and with difficulty to all thefe menfttua . 


it 


2 Dr. Blane’s Account, &c. 

It had a high character among the ancients as a remedy both 
external and internal. It is one m the lift of ingredients in all 
the antidotes, from thofe of Hippocrates, as given on the 
authority of Myrepsus and Nicolaus Alexandrinus, to 
the officinals which have kept their ground till modern times 
under the names of Mithridate and Venice Treacle. It is recom- 
mended by Galen and Alexander Trallian in the droply 
and gravel. Celsus and Galen recommend it both exter- 
nally and internally in pains of theftomach and bowels. 1 he 
firft occafion on which the latter was called to attend Marcus 
Aurelius was when that Emperor was feverely affixed with 
an acute complaint in the bowels, anfwering by the dekription 
to what we now call cholera morbus ; and the firft remedy he 
applied was warm Oleum nardinum on wool to the ftomach. 
He was fo fuccefsful in the treatment of this lllnels, that he 
ever afterwards enjoyed the higheft favour and confidence 

of the Emperor. 

It would appear, that the natives of India confider it as an 
efficacious remedy in fevers, and its fenfible qualities promife 
virtues fimilar to thofe of other fimples now in ufe among us 
in fuch cafes. Befides a ftrong aromatic flavour, it poflefles a 
pungency to the tafte little inferior to th zferpentaria, and much 
more confiderable than the contrayerva. It is mentioned in a 
work attributed to Galen, that a medicine, compofed of this 
and fome other aromatics, was found ufeful m long protra&e 
fevers, which are the cafes in which medicines of this clals 

are employed in modern practice. 

Tab. XVI. is a reprefentation of the Plant. 

t 


rhihu. />«,<., i'„/ i.xxx. rub xvi 





[ 2 93 ] 


XV. An Account of fome extraordinary E feels of Lightning. 
By William Withering, M. D. F. R. S. 

Read March 1 8, 1790. 

P ERMIT me to requeft the attention of the Royal So- 
ciety, whilft I mention a few fa£ts relative to a thunder 
cloud, the lightning from which fufed a quantity of quart- 
zofe matter. 

This cloud formed in the fouth, in the afternoon of Sept. 3, 
1789, and took its courfe nearly due north. In its paflage 
it fet fire to a field of {landing corn ; but the rain prefently 
extinguifhed the fire. Soon afterwards the lightning ftruck an 
oak tree, in the Earl of Aylesford’s park at Packington. 

The heighth of this tree is 39 feet, including its trunk, 
which is 13 feet. It did not flrike the higheft bough, but that 
which projected fartheft fouthward. A man, who had taken 
Ihelter againft the north fide of the tree, was ftruck dead in- 
ftantaneoufly, his cloaths fet on fire, and the mofs ( lichen) on 
the trunk of the tree, where the back of his head had refted, was 
likewife burnt. Two men, fpedlators of the accident, ran 
immediately towards him upon feeing him fall ; and as it rained 
hard, and a fmall lake had collected almoft clofe to the fpot, 
the fire was very foon extinguifhed ; but the efifedts of the fire 
on one-half of his body, and on his cloaths, were fuch as to 

fhew, that the whole burning was inftantaneous, not pro- 
greftive. 

7 


Part 


t)r. Withering’s Account of fome 

Part of the ele&ric matter pafl'ed down a walking flick, 
which the man held in his hand, (loping from him; and 
where the flick refted on the ground, it made a perforation 
about 2 \ inches m diameter, and ^ inches deep, -Tins no,^ f 
examined foon afterwards, and found nothing in it but the 
burnt roots of the grafs. All obfervation would probably have 
ended here, had not Lord Aylesford determined to ereft a mo- 
nument upon the fpot, not merely to commemorate the event, 
but with an infcription, to caution the unwary againft the danger 
of fheltering under a tree during a thunder ftorm. In digging 
the foundation for this monument, the earth was difturbed at 
the perforation before mentioned, and the foil appeared to be 
blackened to the depth of about ten inches. At this depth, a 
root of the tree prefented itfelf, which was quite black ; but 
this blacknefs was only fuperficial, and did not extend far 
along it. About two inches deeper, the melted quartzofe mat- 
ter began to appear, and continued in a hoping direction to 
the depth of 18 inches. 

The fpecimens which accompany this Paper, and for which 
1 am indebted to the attention of Lord Aylesford, will de- 
monftrate the intenfe heat which mud have exifted to bring 
fuch materials into fufion. 

N° i. A quartz pebble, one corner of which has been com- 
pletely fufed. 

2. Sand, unmixed with calcareous matter, agglutinated 
by the heat. Within the hollow part of this mafs, the fuliou 
has been fo perfect, that the melted quartzofe matter has run 
down the hollow, and afiumed nearly a globular figure. 

N° 3. Smaller hollow pieces, and one nearly flat, but all 
the flat ones have fome hollow part *. 

* Thefe fpecimens were laid before the Society when the Paper was read. C. B, 

' Mr. 


extraordinary Effects of Lightning. 295 

Mr. Watt fuggefted to me, that the hollows had been 
occafioned by the expanfion of moifture whilft the fufion 
exifted. 

I (hall conclude with obferving, that judging from the da- 
mage done to the oak tree, the ftroke was not very great ; and 
that having now an inducement to dig where the earth has 
been perforated by lightning, we may probably hereafter find 
foffil fubftances melted by it to a confiderably greater extent. 



/ 


C 29 6 ) 


XVI. An Account of a Child with a double Head. In a Letter 
from Everard Home, Efq. F. R. S. to John Hunter, Efq. 
F. R. S. 


Read March 25, 1790. 

/ 

f'i - 

DEAR s I R, 

I FEEL a particular fatisfa&ion in having been enabled, 
through the kind attention of my Friend Captain Bu- 
chanan, to add to your invaluable colle&ion the very uncom- 
mon double fkull of a monftrous child, born in the Eaft Indies, 
which attracted the attention of all the curious in Calcutta, 
where it was (hewn alive; and, fliould the following account 
of it appear to you of fufficient importance, I (hall requeft 
that you will do me the honour of laying it before the Royal 

Society. 

It is much to be regretted, that the hiftories of monftrous 
appearances in the ftru&ure of the human body which are 
to be found in the works of the older writers, and even of 
many of the moderns, are fo little to be depended upon. Few 
authors have contented themfelves with giving a Ample detail 
of fa£ls that were extraordinary ; but, from an over anxiety to 
make them ftill more wonderful, or from having given an im- 
plicit belief to the accounts received from the credulous and 
ignorant, they have commonly added circumftances too extra- 
vagant to deferve the attention of a reafonable mind, which 

prevent 


Mr. Home’s Account , &c# 297 

prevent the reader from giving credit to any part of the narra- 
tion. This has been fo general, that whenever the hiftory of 
any thing uncommon appears, the rniud is imp relied with a 
doubt of its authenticity, and requires fome ftronger evidence 
of the fafis than the (ingle teftimony of an individual in other 
refpedls unimpeached in his veracity. 

As the hiftories of remarkable deviations from the common 
courfe of nature in the formation of the human body already 
regiftered in the Philofophical Tranfacfions are very numerous, 
1 am defirous of adding to them an account of one fo truly 
uncommon, that, I believe, no fimilar inftance is to be found 
upon record. It is a fpecies of lufus naturae fo unaccountable, 
that, although the faffs are fufficiently eftabliftied by the tefti- 
monies of the moft refpeftable witnefles, I ihould ftill be dif- 
fident in bringing them before the Royal Society, were I not 
enabled at the fame time to produce the double Ikull itfelf, in 
which the appearances illuftrate fo clearly the different parts of 
the hiftory that it muft be rendered perfedlly fatisfaffory to 
the minds of the moft incredulous. 

' l 

The following account of the child, when fix months old, 
I was favoured with from Sir Joseph Banks ; who, from the 
hand-writing, and other circumftances, believes that it was 
written by the late Colonel Pierce. I have, however, been lefs 
folicitous to afcertain the author, as the obfervations contained in 
this account agree fo intirely with the remarks that were after- 
wards made, and with the appearances of the ikull, that they 
require no name being annexed to them, in confirmation of 
their having been made with accuracy and fidelity. 

The child was born in May, 1 783, of poor parents; the 
mother was thirty years old, and named Nooki ; the father 
Vol. LXXX. R r 


was 


2 ^3 Mr. Home’s Account of 

was called Hannai, a farmer at Mandalgent near Bardawan, in 

Bengal, and aged thirty-five. 

• At the time of the child’s birth, the woman who afted as 
midwife, terrified at the ftrange appearance of the double head, 
endeavoured to deftroy the infant by throwing it upon the fire, 
where it lay a fufficient time before it was removed to have one 
of the eyes and ears confiderably burnt. 

The body of the child was naturally formed, but the head 
appeared double, there being, befides the proper head of the 
child, another of the fame fize, and to appearance almoft 
equally perfect, attached to its upper part. This upper head 
was inverted, fo that they feemed to be two feparate heads 
united together by a firm adhefion between their crowns, but 
without any indentation at their union, there being a fmootli 
continued furface from the one to the other. The face of the 
upper head was not over that of the lower, but had an oblique 
pofition, the center of it being immediately above the right eye. 

When the child was fix months old, both of the heads were 
covered with black hair, in nearly the fame quantity. At this 
period the fkulls feemed to have been completely offified, ex- 
cept a fmall fpace between the ofla frontis of the upper one, 

like a fontinelle. 

/ 

Obfervations on the fupenor or inverted head. 

No pulfation could be felt in the fituation of the temporal 
arteries ; but the fuperficial veins were very evident. 

The neck was about two inches long, and the upper part of 
it terminated in a rounded foft tumor, like a fmall peach. 

One of the eyes had been confiderably hurt by the fire,, but 

the other appeared perfect, having its full quantity of motion ; 

but the eyelids were not thrown into a&ion by any thing lud- 

denly approaching the eye ; nor was the iris at thofe times in 

*7 til 6 


a Child with a double Head, 29^9 

the leaft affected ; but, when fuddenly expofed to a ftrong 
light, it contracted, although not fo much as it ufually does. 
The eyes did not correfpond in their motions with thofe of the 
lower head ; but appeared often to be open when the child was 
aileep, and (hut when it was awake. 

The external ears were very imperfeCt, being only loofe folds 
of Ikin ; and one of them mutilated by having been burnt. 
There did not appear to be any paffage leading into the bone 
which contains the organ of hearing. 

The lower jaw was rather fmaller than it naturally fliould 
be, but was capable of motion. The tongue was fmall, flat, 
and adhered firmly to the lower jaw, except for about half an 
inch at the tip, which was loofe. The gums in both jaws 
had the natural appearance; but no teeth were to be feen 
either in this head or the other. 

The internal furfaces of the nofe and mouth were lubri- 
cated by the natural fecretions, a confiderable quantity of mu- 
cus and faliva being occafionally difcharged from them. 

The mufcles of the face were evidently pofleffed of powers 
of action, and the whole head had a good deal of fenfibility, 
fince violence to the fkin produced the diftortion expreffive of 
crying, and thrufting the finger into the mouth made it fhew 
ftrong marks of pain. When the mother’s nipple was applied 
to the mouth, the lips attempted to fuck. 

The natural head had nothing uncommon in its appearance \ 
the eyes were attentive to objects, and its mouth fucked the 
bread: vigoroufly. Its body was emaciated. 

The parents of the child were poor, and carried it about the 
ftreets of Calcutta as a curiofity to be feen for -money ; and to 
prevent its being expofed to the populace, they kept it con- 
stantly covered up, which was confidered as the caufe of its 
being emaciated and unhealthy. 

R r 2 


The 


/ 


,00 Afr. Home’s Account of 

The attention of the curious was naturally attra&ed by fo 
uncommon a fpecies of deformity; and Mr. Stark, who re- 
iided in Bengal during this period, paid particular attention to 
the appearances of the different parts of the double head, and 
endeavoured to afcertain the mode in which the two ikulls 
were united, as well as to difcover the fympathies which 
exifted between the two brains. Upon his return to 
England, finding that I was in poffeliion of the fkull, 
and propofed drawing up an account ci tiie child, he very 
obligingly favoured me with the following particulars, 
and has likewile allowed me to have a fketcn taken 
from a very exa£t painting, made under his own mfpeftion 
from the child while alive, by Mr. Smith, a portrait painter 
then in India. From this drawing, which is annexed, and 
■f^vo others, representing theheans in the natural date , and the 
fkulls, when all the other parts were removed, a much more 
accurate idea will be given or the cmiu s appearance than can 

be conveyed by any defcription. 

At the time Mr. Stark faw the child, it muft have been 
nearly two years old*, as it was Some months before its death, 
which I have every reafon to believe happened in the year 1 785. 
At this period the appearances differed in many refpe&s from 
thofe taken .notice of when only fix months old. 

The burnt ear had fo much recovered itfelf as only to have 
loft about one fourth part of the loofe pendulous flap. The 
openings leading from the external ear appeared as diftinft as 
in thofe of the other head. The fkin furrounding the injured eye, 
which was on the fame fide with the mutilated ear, was in a 

* The dentes molares, or double teeth, which ufually appear at twenty months 
or two years of age, were through the gum $ and there was no reafon to expert 
them very early in this child* 

High 


rt 


a Child with a double Head. ooi 

flight degree affeCled, and the external canthus much con- 
tracted, but the eye itfelf was perfeCt. 

The eyelids of the fuperior head were never completely 
fliut, remaining a little open, even when the child was afleep, 
and the eyeballs moved at random. When the child was 
roufed, the eyes of both heads moved at the fame time ; but 
thofe of the luperior head did not appear to be directed to the 
fame objeCt, but wandered in different directions. The tears 
flowed from the eyes of the fuperior head almoft condantly, 
but never from the eyes of the other, except when crying. 

The termination of the upper neck was very irregular, a 
good deal refembling the cicatrix of an old fore.. 

The fuperior head teemed to fympathife with the child in 

mod of its natural aCtions. When the child cried, the features 

of this head were arfeCted in a timilar manner, and the tears 

flowed plentifully. When it fucked the mother, fatisfaftion 

was expreffed by the mouth of the fuperior head, and the 

faliva flowed more copioufly than at any other time; for it 

always flowed a little from it. When the child fmiled, the 

features of the fuperior head fympathifed in that aftion. When 

the fkin of the fuperior head was pinched, the child feemed to 

feel little or no pain, at lead not in the fame proportion as was 

felt from a fimilar violence being committed on its own head 
or body. 

When the child was about two years old, and in perfedt 
health, the mother went out to fetch fome water j and, upon 
her return, found it dead, from the bite of a Cobra de ca~ 
pelo. The parents at this time lived upon the grounds of 
Mr. Dent, tne honourable Eaft India Company’s Agent for 
Salt at Tumloch, and the body was buried near the banks of 
the Boopnorain river. It was afterwards dug up by Mr. Dent 

1 and 


\ 


02 Mr. Home’s Account of 

and his European fervant, the religious prejudices of the 
parents not allowing them to difpenfe with its being interred. 

My friend, Captain Buchanan, late Commander of the 
Ranger Packet,, in the fervice of the honourable the haft India 
Company, when at Bengal reftded a few days in Mr. Dent s 
houfe. • He was much ft ruck with the uncommon appearance 
of the double Ikull, and expreffed a wifti that he might be 
allowed to bring it to Europe, and prefent it to me ; know- 
, i„g, from the intereft: I have always taken m thole purfuits 
- which have fo long and fo deeply engaged your attention, it 
would be a moft acceptable prefent. His requeft was no fooner 
, communicated to Mr. Dent, than it was complied with ; that 
gentleman having too much liberality to hefitate a moment in 
; fending fo rare a curiofity to Europe. I fhould do both thcle 
gentlemen injuftice, were I not to attribute their readinefs upon 
, the prefent occafion to oblige me, in a great meaiure to their 
knowing that the double ikull would be depofited in your col- 
lection, which muft now be confidered more as a national and 

public repolitory than a private cabinet. 

The two Ikulls which compofe’ this monftrous head appeal 
, to be nearly of the fame fize, and equally complete in their 
ofliiication, except a fmall fpace at the upper edge of the offa 
frontis of the fuperior Ikull, fimilar to a fontinelle. The 
mode in which the two are united is curious, as no portion of 
•bone is either added or diminilhed for that purpofe; but the 
frontal and parietal bones of each Ikull, inftead of being bent 
Inwards, fo as to* form the top of the head, are continued on; 

and, from the oblique pofition of the two heads, the bones of 

the one pafs a little way into the natural futures of the other, 
• forming a zig-zag line, or circular future uniting them toge- 
ther. 


The 


a Child with a double Head. ^ Q ^- 

The two Ikulls appear to be almoft equally perfect at their 
nnion ; but the fuperior Ikull, as it recedes from the other, is 
becoming more imperfedt and deficient in many of its parts. 

The meatus auditorius in the temporal bone is altogether 
wanting. 

The balls of the fkull is imperfect in feveral refpe£ts, par- 
ticularly in fuch parts as are to connect the Ikull with a body. 
The foramen magnum occipitale is a fmall irregular hole, 
very inefficient to give paffage to a medulla fpinalisj round 
its margin are no condyles with articulating furfaces, as there 
were no vertebrae of the neck to be attached to it. The fora- 
men lacerum in bafi cranii is only to be feen on one fide, and 
even there too fmall for the jugular vein to have paffed through. 

The ofla palati are deficient at their pofterior part ; the lower 
jaw is too fmall for the upper, and the condyle and coronoid 
procefs of one fide are wholly wanting. 

In mod of the other refpedts, the two Ikulls are alike ; the 
number of teeth m both is the lame, and is fixteen. i 

From an examination of the internal ftrudfure of the double 
Ikull, the two brains have certainly been inclofed in one bony 
cafe, there being no feptum of bone between them. How far 
they were intirely diftindt, and furrounded by their proper 
membranes, cannot now be afcertained ; but from the fympa- 
thies which were taken notice of by Mr. Stark between the 
two heads, more particularly tiiofe of the fuperior with the 
lower, or more perfeft, I Ihould be inclined to believe, that 
there was a more intimate connexion between them than fimply 
by means of nerves, and therefore that the fubftance of the 
brains was continued into one another. 

Had the child lived to a more advanced age, and given men 
of obfervation opportunities of attending to the effedts of this 

double 


304 Afr. Home’s Account of 

double brain, its influence upon the intelleffual principle muft 
have afforded a curious and ufeful fource of inquiry; but un- 
fortunately the child only lived long enough to complete the 
edification of the fkull fo as to retain its fhape, by which means 
we have been enabled to afcertain and regifter the faff, without 
having enjoyed the fat is faff ion that would have refulted from 
an examination of the brain itfelf, and a more mature invefti- 
gation of the effecfs it would have produced. 

Yours, < 3 :c. 

E. H 0 ‘M E. 

Leicefter- fquare, 

May 22, 1790. 


EXPLANATION OF THE PLATES. 

Tab. XVII. The child is reprefented in this plate as it 
appeared at the age of twenty months, and is copied from a 
piffure in the pofleffion of Mr. Stark. 

The painting was taken from the child fix months before its 
death by Mr. Smith, an ingenious artilf, at that time redding 
in Bengal. 

It conveys a general idea of the appearance of this extraor- 
dinary child, and the relative proportions between the double 
head and the body. 

Tab. XVIII. fig. 1 . In this figure the double head is reprefented 
exaffly half the natural fize. One of the eyes of the upper 
face appears fmaller or more contradfed than the other ; this 
is in confequence of the injury it received when the child was 
thrown upon the fire. 


The 



JZh7o.w Tran.* Vof. LXXX. To(. XVII. />. ;i<> /. 








' ■ » 
















Ml**. Tra,,;. Vvl. L XXX. Tai. XVIlL 



L Hib\ 


a Child with a double Head. ^05 

The fuperficial veins upon the forehead of the upper head 
are very diftinftly feen. 

Fjg. 2. An ex aft reprefentation of the double fkull, which 
is now in Mr. Hunter's collection, upon the fame fcale as 

%. i. 

It fhews the curious manner in which the two fkulls are 

united together, and the number of teeth formed before the 

child’s death ; which circumftance afcertains, with tolerable 
accuracy, its age. 




Vol. LXXX. 


[ 3° 6 3 


X'VII. On the Analyfis of a Mineral Subfance from New South 
Wales. In a Letter from Joiiah Wedgwood, Efq. F. R. S. 
and A. S, to Sir jofeph Banks, Bart. P. R. S. 


Read April 15, 1790. 

DEAR SIR, Etruria, March 12, 1790,- 

1 HAVE the pleafure of acquainting you, that the clay 
from Sydney-Cove, which you did me the honour of lub- 
netting to my examination, is an excellent material for pot- 
tery, and may certainly be made the balls of a valuable manu- 
fafture for our infant colony there. Of the fpecies of ware 
which may be produced from it, you will have fome idea from 
the medallions I have fent for your infpe&ion. 

The other mineral, which you favoured me with a fpecimen 
of, feems to me to contain one fubftance hitherto unknown, 
and another not known in the Rate of purity in which it is 
here found. I (hall therefore take the liberty of ftating, as 
concifely as I can, the principal refults of the experiments that 
have been made upon it by myfelf and my affiftant Mr. 
Chisolm ; Submitting it to your judgement, whether any of 
them be of Importance enough to be laid before the Royal 
Society. 

I have the honour to be, &c. 

JOS. WEDGWOOD. 

Analytical 


Mr. Wedgwood's Analyfn , & c . w 

Analytical experiments on a Mineral from Sydney-Cove in 

New South Wales. 

THIS mineral is a mixture of fine white fand, a foft white 
earth, fome colouriefs micaceous particles, and a few black 
ones refembling black mica or black-lead; partly loofe or de- 
tached from one another, and partly cohering together in little 
rriable lumps. 

. None of thefe fubftances feem to beat all a£);ed upon by the 
nitrous acid, concentrated or diluted ; nor by oil of vitriol di- 
luted with about equal its meafure of water ; in the cold, or 
m a boiling heat ; the mineral remained Unaltered in its ap- 
pearance, and the acids had extra&ed nothing from it that 
could be precipitated by alkali. 

Oil of vitriol boiled upon the mineral to drynefs, as in the 
procefs of making alum from day, produced no apparent 
c ange in it ; but a lixivium made from this dry naafs with 
water, on being faturated with alkali, became fomewhat tur- 
bid, and depofited, exceeding flowly, a white earth in a gela- 
tinous ftate, too fmall m quantity for any particular examina- 
tion ; but which, from its afpedt, from the manner in which 
it was obtained, and from the tafte of the lixivium before the 
addition of the alkali, was judged to be the aluminous earth. 

The marine acid, during digeftion, feemed to have as little 
action as the other two ; but on pouring in fome water, with a 
view only to dilute and wafh out the remaining part of the acid 

a remarkable difference prefented itfelf; the liquor became in- 

ftantly white as milk, with a fine white curdly fubflance in- 
termixed; the ftrong acid having extracted fomething which 
the fimple dilution with water precipitated® 

S f 2 


The 


^ 0 g Mr. Wedgwood’s Analyfis of a 

The white matter being walhed off, more fpirit of fait was 
added to the remainder, and the digeftion repeated, with a long 
tube inferted into the mouth of the glafs, fo as nearly to pre- 
vent evaporation. The acid, when cold and lettled fine, was 
poured off clear ; and on diluting it with water, the fame 

milky appearance w'as produced as at firft. 

The digeftion was repeated feveral times fucceffively, wit \ 
frelh quantities of the acid, till no milkinefs appeared on di- 
lution. The quantity of mineral employed was 24 grams ; 
and the refiduum, after the operations, walhed and dried, 
weighed fomewhat more than 19 grains; fo that about one- 
fifth of it had been diffolved. In feme parcels ot the mineral, 
taken up promifeuoufly, the proportion of foluble matter was 
much lefs, and in none greater. It is only the white part, an 
only a portion of this, that the acid appears to ad upon : the 
white fand, much of the white foft earth, and all the black 

particles, remain unaltered. 

To try whether this tedious procefs of folution could be ex- 
pedited by triture or calcination, fome of the mineral was 
rubbed in a mortar ; and in doing this, it appeared pretty re- 
markable, that though the black part bore but an inconfidera- 
ble proportion to the reft, yet the whitenefs of the other was 
loon covered and fupprefled by it, the whole becoming an 
uniformly black, Ihining, foft, unduous mafs, like black- 
lead rubbed in the fame manner ; with a few gritty particles 
perceptible on preffing hard with the peftle. A penny-weight 
of this mixt, fpread thin on the bottom of a porcelain veffel, 
was calcined about an hour, with a fire between 30 and 40 

degrees * ; it became of an uniform, dull, white, or grey colour, 

b excepting 

* Bv decrees of fire, or of heat above ignition, I mean thofe of my thermo. 

J ® meter 5 


Mineral Subflance from New South Wales. sqq 

excepting a very few, and very fmall, fparkling, black particles, 
fufpedled to be thole which had eluded the adtion of the pellle ; 
it loft in weight fix grains, or one-fourth. 

The mineral, thus ground and calcined, was found to be 
juft as difficult of folution as in its crude ftate ; with this 
additional difadvantage, that the undiflolved fine particles are 
indiipofed to fettle from the liquor. 

In all the experiments of diflolution, as often as the heat 
was at or near the boiling point of the acid, frequent, and 
pretty fingular, burfts or explofions happened, though the 
matter lay very thin in a broad-bottomed glafs. They were 
fometimes fo confiderable as to throw off a porcelain cup with 
which the glafs was covered, and once to lhatter the glafs in 
pieces. Ill a heat a little below this, the extraction feemed 
to be equally complete, though more flow; but a heat a little 
below that in which wax melts, or below 140° of Fahren- 
heit s thermometer, appeared infufficient. 

To determine the degree of dilution neceffary for the preci- 
pitation of the diffolved fubftance, and whether the precipita- 
tion by water be total, a meafure of the folution was poured 
into a large glafs, and the fame meafure of water added 
repeatedly. The third addition of water occafioned a flight 
milkinefs, which increafed more and more to the fixth. The 
liquor being then filtered off, another meafure of water pro- 
duced a little freffi milkinefs ; and an eighth rather increafed 
it ; a ninth and a tenth had no effedh The liquor being now 
again palled through a filter, folution of fair of tartar did not 
m the leaft alter its tranfparency ; fo that, after the folution 

meter; and feme idea maybe formed of their value, by recollecting, that they 
commence at viable rednefs ; and that the extreme heat of a good air-furnace 
w the common conftruaion, is 160°, ora little more. 


has 


'Mr. 'W edgwood’s Analyfs of a 
has bee,, dilated with eight or nine times its me.fi.re of water, 
there is nothing left in it that alkali can precipitate. 

From the manner in which the folnt.on ,s neceffarily pie- 
pared, it cannot but contain a great redundance of acid ; for 
the fmall quantity of acid, fnfficieut for holding the foluble 
part fufpended, would be foaked op or entangled by the undif- 
folved part, ffo as fiercely to admit of any being poured off, and 
it cannot be diluted, or walh.d out, but by the ftrong and 
itfelf. The folution with which the above experiment was 
made was reckoned to have only about fix grams of the foluble 
matter ,0 three ounces of fpirit of fall, having been prepared 
by digefting that quantity of the fpi.it by half an ounce at a 

time on thirty grains of the crude mineral. 

A Saturated folution was obtained by dige nig, m a 

portion of the Motions thus prepared, the 
down by water from the larger portions till the acid would 
take up no more. A folution, thus faturated, cannot bear the 
tolled quantity of water, a Ragle drop, on the full contact, 
producing a milky circle round it. 


zxam im t m of the above fubfance, extraM from lb, mineral b, 
marine acid, and precipitated by water . 

This fubftance, wafhed and dried, is indiffoluble in 
s indeed might be expected from the manner of its pr.pa- 

" Nor is it afled upon by the nitrous or vitrKdic^^nDC®- 

:,ated or diluted, colder hot; nor by alkaline foluttons, 

, r rauftic, of the volatile or fixed kin . . , . 

ut iw by ftrong if **- •*. ** £ 

afliftance of nearly the ° From , Ms folution it is 

for its extradion from the min nreC imtated 


I 


Mineral Subftance from New South Wales. , n 

precipitated by water; and, after repeated diffolutions and 

precipitations, it appears to have buffered no decompofition or 
change. 

Spirit of nitre, added to the faturated folution, makes no 
precipitation; and if the quantity of nitrous acid exceeds, or 
at leaft does not fall much fhort of, that of marine acid in the 
folution, the mixture buffers no precipitation from water. Nor 
does any precipitation happen, though the nitrous fpirit be 
previoufy mixed with even a large quantity of wafer; provided 
the quantity of folution added to it does not exceed that of the 
nitrous fpirit im the mixture. The appropriate menftruum for 
this fubftance (that is, for keeping it in a ftate of dilute folu- 
tion) appears therefore to • be aqua regia; and the due propor- 
tions of the two acids, of any given ffrength, might be deter- 
mined, if neceffary, with greater accuracy and facility for 
this than for any other body I know of; becaufe, if there be 
even a very minute furplus of marine acid in the folution, 
that furplus will inffantly betray itfelf on dropping a little into 
water, all that was diffolved by it, and no more, being preci- 
pitated by the water. It may be oblerved, j however, that 
where an addition of nitrous acid is ufed, a faturated folution 
cannot be obtained (unlefs by fubfequent evaporation), the fame 
quantity of marine acid being neceffary with as without that 
addition: the change, or modification, which the nitrous acid 
produces in the marine, ferves, in the prefent inftance, not for 
effeding the folution, as in the cafe of gold and fome other 

metals, but merely for enabling it to bear water without depo- 
futing its contents. 

Oil of vitriol, dropped into the faturated marine folution, 
occafions no change till its quantity comes to be about equal to 
that of the folution j a confiderable effervefcence and heat are 

then i 


Mr. Wedgwood’s Analyjis oj a 
IL produced, the liquor becomes milky, sod .lie marine acid 
is extricated in its ufual white fumes. The mixture, hea e 
nearly to boiling, becomes tranfparent, and afterwards Con- 
Lues fo in the cold. This vitriolic folution rs prec, prated by 

water, and the precipitate is ,e-diflolved by 

The faturated marine foliation is indifpofed to cryfta hze. y 
continued evaporation in gentle heat, it becomes thick arid 
butyraceous, and in .bis (late it boon LqueSes agan^on exp - 
Pure to the air. The butyraceous mafs, in colour wh.t.lh 
p“ e Yellow, is no. corrolive, like the l.mrlar preparations 
mldeVrom fome metallic bodies; nor is it more 
tafte but rather lefs fo than the combination of the lame acid 
with calcareous earth. In a heat increafed nearly to.gmt.on, 
the acid is difengaged, and rifos in white fumes, which re- 
ceived in a cold phial, condenfe into colourlefs drops without 
anv appearance of fublimate. From the remaining white mafs, 
fpirit of nitre extrafts fo little as to exhibit only a (light milki- 
S on adding alkali ; a proof that nearly all the marine acid 
had been expflled ; for, while that acid remains, the whole is 

diffoluble by the nitrous. Prilffian 

The fubftance m quettion is not precipitated by Pruffian 

lixivium. A drop or two of the lixivium do indeed occafion 

little white or bluilh- white precipitation in the faturated m - 

i„e folution , but in the more dilute no turbicfoefs appears t 

the quantity of lixivium is fuch as to produce that effeft by 

mere water; and when the' precipitate has at lengt een 

formed, it re-diflblves in marine acid as eafily as that made y 

water ; whereas the precipira.es refulting from d g urnet, of 

the Pruffian matte, are not afted upon by auds, nil ' that mat 

t «r has been ex, rafted from them by an alkah. For f rthet 

fatisfaftion in this important pomt, the “P”‘ ro 


I 


'■'TO 


Mineral Subfiance from New South Wales. 

repeated with a foliation in aqua regia. Here the Pr.yflian lixi- 
vium, in whatever quantity it was added, cccafioned no preci- 
pitation at all (only the ufual bluifhnefs, arifing from the iron 
always found in the common acids) ; and pure alkali, added 
afterwards, precipitated the original white fubftance unchanged. 

The following experiments of precipitation by alkalies were 
made with the marine folution, before the effeft of an addition 


of nitrous acid had been difcovered ; and they were made with 
fo much care and attention, that it was not thought necefiary 
to repeat them afterwards. To obviate, as much as pofh'ble, 
the equivocal refults that might ante from water contained in 
the precipitants, the different alkalies were applied in the dryeft 
ftate I could reduce them to ; viz. pure fait of tartar , kept for 
fome time in a heat juft below rednefs ; cryftals of marine ah 
kali, melted and dried in the fame manner ; volatile alkali in 
cryftals, a little furplus acid being, in this inftance, previoufly 
added to the folution, to counteraft the water of cryftallization 


in the alkali ; fait of tartar caufiicated by quicklime, and 
haftily evaporated to drynefs ; the marine alkali 'caufiicated in 
like manner ; and the vapour of cavjhc volatile alkali arihng, 
with a very gentle heat, from a retort into a phial containing 
the folution. All thefe alkalies occafioned copious precipita- 
tions. All the precipitates, after wafhing and drying, were 
found to re-diflolve in marine acid ; and, from all thefe folu- 
lions, the original fubftance was precipitated, unaltered, on 
diluting them with water. 

In ftrong fire, from 142 to 156 degrees, this fubftance diT 
covers a much greater fuftbility than any of the known Ample 
earths. In a fmali veffel, made of tobacco-pipe clay, it melted, 
and glazed the bottom ; and on a bed of powdered flint, prefled 
Vol. LXXX. T t fmooth 


_ Ur, Wedgwood’s Analyfil of A 

Loth in the manner of a cupel, * did the fame Magneha 
or chalk, would indeed vitrify in the clay veffel; out on flmt, 
no one of the known earths fhews any tendency to V.tnhcauon 
in that heat K In a cavity, fcooped in a lump of clnU . this 
fubftance, in the heat above mentioned, run _ into a ma 
roundhead, fmooth, whitilh, and opaque, not: ml the lea a - 
hering to the calcareous mafs. On a bed of powdered quick- 
lime ft formed i browffiffi (tom, which in great par, WM 
into the lime, and feemed to have united with it. On dr. 
Henry’s maguefia, uncalcined, it melted and funk m com- 
pletely, leaving only a flight brownhh ftam on the furface 
where it had lain. On beds of the barofehmte and baryt.c 
quicklime, it hkewife melted and funk in, leavmg a d.ico- 
Lred foot behind; but whether it really umted with the fub- 
ftrata or only penetrated into their interfaces, could not be 
determined with certainty, on account of the fmallnels of the 

quantity of the mineral 1 had to work upon. 

On a bed of powdered charcoal, in a crucible clofely lu e , 

this fubftance likewife melted ; and therefore it may be pre- 

* It may be proper juft to mention, that I find this to be a very commodious 
and fnre method of trying, in fmall, whether any given earthy body be fufi le 
with other earths. If the body is difpofed to vitrify with any proportion of clay 
or flint, for inftance, it will equally vitrify when a little of « » apphed or even 
dufted only, on the bottom of a fmall cup made of clay, or on a fmooth clofe bed 
^ finely powdered flint. The body, in this mode of applicanon, feems to unite 
with only juft fo much of the matter of the fubftratum as is reqmfite for them 
rooft p. r fea fufion together, and has nothing elfe m contaft with n, to t ha. no 
deception canarife; whereas, if mlx'J with the fame matter, there mtght be no 
, ppe Lnce of fufion, unlefs certain favourable proportions of the two fiiouU 
Chance to be hit upon ; and even then, if the quantity be fmall, it would no 
certain but that the fufion might have originated from the matter of the cruc.bK 


Mineral Subfiance from New South Wales. $t 

fumed not to have owed its fufion, in the above experiments, 
to the fame caufe to which fome of the common fimple earths, 
in certain circumftances, owe theirs, namely, their union with 
the matter of the vefle.1 or fupport, that is, with an earth or 
earths of a different kind from themfelves ; but to poflefs a 
fufibility ftridtly its own, which takes place in afire of 150 
degrees, or perhaps lefs. 

As charcoal in fine powder affumeS a kind of fluidity in the 
fire, fulfil ar to that which powdered gypfum exhibits in a fmali 
heat, its furface had changed from concave to horizontal, and 
the bead had funk to the bottom ; it was rough and black on 
the outfide, and whitifh within. On repeating the experiment 
in a cavity fcooped in a piece of charcoal, the refult was a 
blackifh bead like the former, only fmooth on the outfide, with 
fomething of metallic brightnefs, not unlike that of black- 
lead. Both beads were very light, and had a confiderable ca- 
vity within. All the internal part was whitifh, without the 
leaft metallic afpeft ; and the external gloffy blacknefs appeared 
to be only the fcain which charcoal powder communicates, in 
ftrong fire, to fome earthy bodies that have a tendency to 
vitrify. By boiling in concentrated marine acid a part of the 
beads was diffolved, precipitable as at firft by water ; but an, 
accident prevented the procefs from being continued fufficiently 
to determine whether the whole could be diffolved or not. 

By this fufibility in the fire ; folubility in one only of the 
Common mineral acids, and parting with the acid in a heat 
below ignition ; precipitability by water, and non-precipita- 
bility by Pruffian lixivium ; this fubftance is ftrongly diferimi- 
nated from all the known earths and metallic calces. And as 
it fuffers no decompofition from any of the alkalies, in any of 

T t 2 the 




„ 5 g Mr. Wedgwood’s Analyfis of a 

the ufual modes of application, 1 prefame, it cannot be confi- 
c’cred as a combination of any ot thole earths 01 calces with 
any 0 f the known acids; for all the combinations of this kind 
would, in one or other of the above methods of trial, have 
had the earth or metal difengaged from the acid. 

Whether this fubftance belongs to the earthy or metallic clafs, 
I cannot abfolutely determine ; but am inclined to refer it to 

the earthy; becaule, though brought into perteft tuhon, m 
contact with inflammable matter, and in dole vtflds, it does 
not aflume the appearance which metallic bodies do in that 

circumftance. 


Examination of the black particles . 

Thefe particles, which bore but a very fmall proportion to 
the other matter, were in form of Alining black leaks, very 
thin, and very light. One grain weight of them, carefully 
picked out, expofed to a fire which was gradually railed to 
about 90°, and continued in all about 40 hours, 111 a veflel 
loolely covered, was almoft wholly diffipated, and what little 
remained was perfectly white. Marine acid had no effect on 

It. 

Fifteen grains of the entire mineral loft, in the fame fire, 
three grains. After ieparating from another portion of the 
mineral, by waffling and otherwife, a confiderable quantity of 
the white matter, 1 5 grains of the remainder, containing of 
courfe more than its due proportion of the black,, loft five grains ; 
fo that it feems principally to be the fubftance 011 which the 
blacknefs depends that is deftroyed or diffipated by fire. The 
fame quantity, 1 5 grains, of common black-lead loft in the fame 

fire above 14 grains, the refiduum weighing lei's than one grain. 

Though 


Mineral Subjiance from New South Wales. jrj- 

Though no conclufion can be drawn from thefe experiments 
refpedting the comparative lojs of black-lead and the pure black 
matter of this mineral, on account of the heterogeneous parts 
intermixed with the latter, the colour of the refidua fee ms to 
afford a, fufficient difcrimination between them ; that of black* 
lead being dark rcddiffv brown, but the others purely and uni- 
formly white*. 

As this fubftance could not now be fuppofed to be either 
iron mica, or the common kind of black-lead, fufpicion fell 
upon ■. molybdasna. I had not, at that time, had an opportunity 
of procuring a fpeeimen of molybdama to compare it with 
but from the Angular and ftrongly-marked properties of the 
molybd^nic acid, difcovered by Scheele, it was judged, that 
a very fmail quantity of it, when di (engaged .from the fulphur 
with which it is naturally combined, would eaiily be diftin- 
guifhable. 

H jelm’s procefs for difengaging the fulphur, by repeatedly 
burning lihfeed oil upon the molybdaena in a crucible, and 
afterwards abflrafting fucceffive quantities of the fame oil from 
it in a retort, was tried on a portion of the Sydney-C.ove mi- 
neral, from which much of the white matter had been fepa- 
rated as above mentioned. The -black coal, remaining in the 
retort, became yellow by calcination, as that of molybdaena 
fhould do ; but in this yellow powder, no veftige of moiyb^ 
d^nic acid could be difcovered. 

Another quantity of the mineral, was fubmitted to ScheeleY 
own procefs, vm. repeated abftradlions of diluted nitrous acid ; 
but, inftead of becoming whiter every time, and at length 
white as chalk, which molybdaena fhould do, the blackneis of 
this matter continued unaltered to the lafb 


There, 


, 3 Mr. Wedgwood’s Analyp of a 

There is one circumftance in Mr. Scheele's experiments, 
which, though omitted by thofe who have given abftrafts of 
them, may deferve, on the prefer* occaficn, to be more parti- 
cularly noticed. He reduced the molybdaena into fine powder, 
and poured upon it concentrated nitrous ac.d: “ mixture 
he fays, was hardly lukewarm in the retort, when it pafled all 
“ together into the recipient with great heat ; an t was or 
this reafoti that he afterwards ufed diluted acid. 1 refum.ng 
that this violent aftion of the concentrated nitrous acid m.ght 
afford a decifive criterion of molybdaena, I a t e ac - re l 
duum, after five or fix abftraftions of the diluted aci , groun 
fine upon a levigating glafs, and returned into the retort, with 
fix times its weight of fmoking fpirit of mtre. The heat was 
increafed cautioufly far beyond lukewarm, but no comrootioi 
could be perceived, except the explofions already mentioned, 
which always took place when the mixture was near boilmg. 
The diftillation was continued to drynefs, and repealed fie 
times with the fmoking acid ; but the mineral remained juft 

black as it was at firft. , 

Now, as Scheele’s rholybdaena is (lowly decompofed by the 

diluted nitrous acid, and rapidly afled upon by the , concen- 
trated acid, while the black part of this mmeral obft.na tely 
refifts both, I think we cannot hefitate to conclu e, - 
Mack fubftance is not Scheele’s molybdarna. There are feme 
other circnmftances which confirm this concluf.on, although, 
finely, they would not, perhaps, be of much werght 
ordering the gLt proportion of other matter tee m.xe 
with the black. The principal of thefe c.rcumtac a , that 
vields no flowers before a blowpipe, and that its p 
' feem to have no flexibility or elafticity, the only dtfficu y^ 


Mineral Suhjlance from New South Wales. 

6f reducing it into fine powder arifing from a property of ano- 
ther kind, unttuofiry. 

The difference, above taken notice of, between this blade 
matter and common black-lead, confifts only in the former 
leaving on calcination a white fubftance, feemingly filiceons, 
and the latter a brown ferrugineous one. In their afped, 
tmftuofity, refiftance to acids, and the volatility (in open fire) 
of that part in which the blacknefs confifts, they perfectly 
agree; and they appear to agree alfo in the nature or conftitu- 
tion of this volatile part ; for the Sydney-Cove mineral, as 
well as black-lead, deflagrates and effervefces very ftrongly 
with nitre, produces an hepatic impregnation on fufion with 
vitriolated alkali, but none with pure alkali, and is manifeftly 
rich in inflammable matter, without fulphur. 

It feems, therefore, that this fubftance is a pure fpecies of 
plumbago, or black-lead, not taken notice of by any writer 
I have met with, Fourcroy, in the laft edition of his Che- 
miftry, looks upon iron as an effential component part of 
black-lead, to which, accordingly, he gives a new name ex- 
preffive of that metal, cdrbure de fer. Lavoisier, in his 
Elements of Chemiftry, lately publifhed, mentions a carbure 
of zinc alfo, and fays that both thefe carbures are called plum- 
bago, or black-lead. The quantity of mineral I had been fur- 
nifhed with was too far exhaufted, before I met with this ob- 
fervation, to admit of any further experiments, for determining 
the prefence of zinc in it ; but thofe already ftated, with the 
recolle£lion of fome circumftances attending them, perfuade 
me, that that metallic body has no Ihare in its compofition. 
Neither before the blow-pipe, nor in calcination, was there 
any appearance of the peculiar flame, or flowers, by which 


zinc 


Mr. Wedgwood’s Anahjis , &c. 
ziric isfo ftrongly charaderifed : if an. fuch appearance had 
taken place, it could not have efcape notice, as tome of the 
calcinations were particularly attend to during the procefs, 
though with d different view, the difeo /c y of l alphur or arfemc. 
The white matter which remains after the catenation 

is certainly not calx of zinc, for it was not aded on by tpmt 

of fait, cold or hot, while the calces of zinc are diffo 
rapidly by that acid, even in the cord. 



[ 3 « 3 


XVIII. Report on the bejl Method of proportioning the TLxcifi 
upon Spirituous Liquors , By Charles Blagden, M. D • Sec . 
R, S. and F, A , S. 

Read April 22, 1790, 

, \ 

PART I. 

On the Experiments. 

, \ 

I N confequence of an application from Government to Sir 
Toseph Banks, Bart. Prefident of the Royal Society, for 
the heft means of afcertaining the juft proportion of duty to be 
paid by any kind of fpirituous liquor that fhould come before 
the Officers of Excife, I was requefted by that Gentleman 
to affift in planning the proper experiments for this purpofe, 
and to draw up the Report upon them when they ftiould be 
finiffied. 

Though various indications of the ftrength of fpirituous li- 
quors have been devifed, applicable in a grofs manner to general 
ufe, it is well known that no method admits of real accuracy but 
that of the fpecific gravity. The weights of an equal bulk of 
water and pure fpirit differ from one another by at leaft a fixth 
part of the weight of the former; whence it is obvious, that, 
when thofe two fluids are mixed together, the compound muff 
have fome intermediate fpecific gravity, approaching nearer to 
that of water or pure fpirit, as the former or the latter is the 
y 0 L. LXXX. U u 


more 


22 Dr. BtAGDEN’s Report 

more predominant ingredient. V\ere it not for a certain 
efftdc attending the mixture of water and 1 pints which has 
been called their mutual penetration, the fpecihc gravuy of 
thefe compofitions, in a given degree of heat would be Amply 
in the arithmetical proportion of the quantity of each of the 
fluids entering into them. But whenever different fubftances, 
which have a ftrong tendency to unite together, are mixed, tne 
refulting compound is found to occupy lefs ipace than the mo- 
ftances forming it held in their i'eparate fldte, wherefore t e 
fpecife gravity of fuch compounds is always greater than would 
be riven by a fimple caculation from the volume of their in- 
gredients. Though it be a general faff, that Inch a decreaie o 
bulk takes place on the mixture of fubftances which have a 
chemical attra&ion for each other, yet the quantity of t ns 
diminution is different in them all, and, under our prefent 
ignorance of the intimate compofition of bodies, can be deter- 
mined by experiment only. To afeertain, therefore the quan- 
tity and law of the condensation refulting from this mutual 
penetration of water and fpirit, was the firft object to which 

the- following experiments were directed. _ 

All bodies, in general, expand by heat ; but the quantity o 
this expanfion, as well as the law of its progrefiion, are pro- 
bably not the fame in any two fubftances. In water and lpmt 
they are remarkably different. The whole expan lion of pure 
fpirit from 30° to ioo° of Fahrenheit’s thermometer, is 

not lefs than -J T th of its whole bulk at 3 °° 5 whereas tha *.° 
water, in the fame interval, is only ^- 5 th of its bulk. 1 be 

laws of their expanfion are ftill more different than the quanti- 
ties. If the expanfion of quickfilver be, as ufual, taken for 
the ftandard (our thermometers being conftruaed with tha 
fluid), the expanfion of fpirit is, indeed, progreflively mcr « - 


on Spirituous Liquors* J23 

ing with refpedl to that standard, but not much fo within the 
above-mentioned interval ; whilft water kept from freezing to 
30% which may eaiiiy be done, will abfolutely contrafl: as it is 
heated for ten or more degrees, that is, to 40° or 42° of the 
thermometer, and will then begin to expand as its heat is 
augmented, at firft (lowly, and afterwards gradually more ra- 
pidly, fo as to obferve upon the whole a very increafing pro- 
greffion, Now, mixtures of thefe two fubftances will, as 
may be fuppofed, approach to the lefs or the greater of thofe 
progreffions, according as they are compounded of more fpirit 
or more water, whilft their total expanfion will be greater^ 
according as more fpirit enters into their competition ; but the 
exa6t quantity of the expanfion, as well as law of the pro- 
greffion, in all of them, can be determined only by trials* 
Thefe were, therefore, the two other principal objects to be 
afceriained by experiment. 

The firft ftep towards a right performance of the experi- 
ments was to procure the two fubftances with which they were 
to be made as pure as poffible. Diftilled water is in all cafes 
fo nearly alike, that no difficulty occurred with regard to it; 
but the fpecific gravity of pure fpirit, or alcohol, has been 
given fo very differently by the authors who have treated of it$ 
that a particular fet of experiments appeared neceffarv for de- 
termining to what degree of ftrength rectified {pints could 
conveniently be brought. The perfon engaged to make thefe 
experiments was Dr. Dollfuss, an ingenious Swifs gentle- 
man then in London, who had diftinguifhed himfelf by feve- 
ral publications on chemical fubjefts. Dr. Dollfuss, having 
been furniffied by Government with fpirit for the purpofe, 
re&ified it by repeated and (low diftillations till its fpecific 
gravity became ftationary in this manner of operating : he then 

U u 2 added 


224 Dr. Blagden’s Report 

added dry cauftic alkali to it, let it (land for a few days, poured 
off the liquor, and difcilled it with a fmall addition of burnt 
alum, placing the receiver in ice. By this method he ob- 
tained a fpirit whofe fpecific gravity was ,8iS8 at 6cr of heat. 
Perceiving, however, that he could not conveniently get the 
quantity of fpirit he wanted lighter than ,82527 at 60% he 
fixed upon that ftrength as a ftandard, to which he found the 
above-mentioned lighter fpirit could be reduced by adding to 
It a _44._g.th part of water ; and with this fpirit and diftilled 
water he made a feries of experiments for determining the 
fpecific gravity of different mixtures of thefe fluids in different 
degrees of heat. 

The procefs followed by Dr. Dollfuss is not here given as 
the beft poflible for obtaining pure fpirit ; nor was the relult of 
it, in fadt, the lighted: alcohol that has been procured. Some 
fpirit has been tried fince that time, whofe lpecific gravity was 
,813 at 6o°. This was furnifhed by Dr. George Fordyce, 
F. R. S. who fucceeded in bringing it to that ftrength chiefly 
by adding the alkali very hot. Care muft be taken that none 
of the cauftic alkali comes over in the diftillation. Some alco- 
hol was alfo fent, for trial, by Mr. Lewis, an eminent diftil- 
ler in Dolborn, whofe fpecific gravity, at the lame tempeia- 

ture, was ,814. 

It was with fpirit rectified from malt-fpirits that Dr. Doll- 
fusses feries of experiments was made ; but he tried feveral 
comparative experiments with fuch as had been redlified from 
rum and brandy, and found no other difference than might 
fairly be afcribed to unavoidable errors. 

Upon examining the refults of Dr. Dollfuss’s experiments 
it was perceived, that though the numbers agreed together 
tolerably well upon the whole, yet in fome places there was 


► 


on Spirituous Liquors* 325 

that degree of irregularity in the firft differences as made it ad- 
vifable to repeat ieveral of the experiments ; and Dr. Doll- 
fuss leaving England about that time, the bufinefs of this re- 
petition was intruded to Mr. Gilpin, Clerk of the Royal So- 
ciety. This gentleman had already taken a part in the bufinefs, 
by affifting Dr. Dollfuss in the former experiments, parti- 
cularly in the very nice part of weighing the mixtures ; and 
his great (kill, accuracy, and patience, in conducing experi- 
ments, as well as in computations, had on other occasions been 
proved to many Members of the Society. One experiment 
leading on to another, Mr. Gilpin was at length induced to go 
through the whole feries anew ; and as the deductions in this 
Report will be taken chiefly from that laft fet of experiments, 
it is proper here to defcribe minutely the method obferved by 
Mr. Gilpin in his operation. This naturally refolves itfelf 
into two parts, the way of making the mixtures, and the way 
of afcertaining their fpecific gravity. 

1. The mixtures were made by weight, as the only accu- 
rate method of fixing the proportions. In fluids of fuch very 
unequal expanfions by heat as water and alcohol, if meafures 
had been employed, increafing or decreafing in regular propor- 
tions to each other, the proportions of the mafles would have 
been fenfibly irregular ; now the latter was the objeCt in view, 
namely, to determine the real quantity of fpirit in any given mix- 
ture, abftraCting the confideration of its temperature. Refides, if 
the proportions had been taken by meafure, a different mix- 
ture Ihould have been made at every different degree of heat. 
Rut the principal confideration was, that with a very nice ba- 
lance, fuch as was employed on this occafion, quantities can be 
determined to much greater exaCtnefs by weight, than by any 
practicable way of meafurement. The proportions were, there- 
fore, 


Dr. Blagdeh’s Report 

fore, always taken by weight. A phial being provided of fuch a 
fise as that it Should be nearly full with the mixture, was made 
perfeaiy clean and dry, and being counterpoised, as much of the 
pure fpirit as appeared necefl’ary was poured into ir. The weight 
of this fpirit was then afcertained, and tne weight ot dil'tilhd 
water, required to make a tnixture of the intended propoition®, 
was calculated. .This quantity of water was then added, with 
all the neceffary care, the laft portions being put in by menus 
of a well known inftrument, which is compofed ot a lmall 
dilh terminating in a tube drawn to a fine point : the top of 
the difh being covered with the thumb, the liquor in it is 
prevented from running out through .the tube by the preiluie 
of the atmofphere, but inftantly begins to iffue by drops, or a 
very fmall ftream, upon railing the thumb. Water being thus 
introduced into the phial, till it exatfly counterpoised the 
weight, which, having been previoufly computed, was put into 
the oppolite fcale, the phial was fhaken, and then well flopped 
w ith its glafs flop pie, over which leather was tied very tight, 
to prevent evaporation. No mixture was ufed till it had re- 
mained in the phial at leaf!: a month, for the full penetration 
to have taken place ; and it was always well fhaken before it 
was poured out to have its fpecific gravity tried. 

2. There are two common methods of taking the fpecific 
gravity of fluids ; one by finding the weight which a folid body 
lofes by being immerfed in them ; the other by filling a con- 
venient vefl'el with them, and afcertaining the increafe of 
weight it acquires. In both cafes a Standard muft have been 
previoufly taken, which is ufually diftilled water ; namely, m 
the firft method by finding the weight loft by tjie folid body 
in the water, and in tne Second method, the weight of the 


on Spirituous Liquors T 
veflel filled with water. The ktter was preferred for the 


3 2 7 


following reafons. 

When a ball of glafs, which is the propereft kind of folid 
body, is weighed in any fpiritnous or watery fluid, the adhe- 
fion of the fluid occafions feme inaccuracy, and renders the 
balance comparatively fiuggifh. To what degree this effedt 
proceeds is uncertain ; but from fome experiments made by 
Mr. Gil, PIN, with that view, it appears to be very fenfible. 
Moreover, in this method a large iurface muft be expo fed to 
the air during the operation of weighing, which, efpecially in 
the higher temperatures, would give occafion to fuch an eva- 
poration as to alter eflentially the ftrength of the mixture. It 
feemed alfo, as if the temperature of the fluid under trial 
could be determined more exadtly in the method of filling a 
veflel, than in the other: for the fluid cannot well be ftirred 
while the ball to be weighed remains immerfed in it ; and as 
fome time muft neceffarily be fpent in the weighing, the change 
of heat which takes place during that period will be unequal 
through the rnafs, and may occafion a feniible error. It is 
true, on the other hand, that, in the method of filling a veflel, 
the temperature could not be ascertained with the utmoft pre- 
cifion, becauie the neck of the veflel employed, containing 
about ten grains, was filled up to the mark with fpirit not 
exactly of the lame temperature, as will be explained pre- 
fently ; but this error, it is luppoied,, would by no means equal 
the other, and the utmoft quantity of it may be eftimated very 
nearly. Finally, it was much ealier to bring the fluid to any 
given temperature when it was in a veflel to be weighed, than 
when it was to have a folid body weighed in it ; becaufe in the 
former cafe the quantity was fmaller, and the veflel contain- 


2 2 8 Dr. Bladen s Report 

j H <r it more manageable, being readily heated with the hand 
or°warm water, and cooled with cold water : and the very cir- 
cumftance, that fo much of the fluid was not required, proved 
a material convenience. The particular difadvantage in the 
method of weighing in a veffel, is the difficulty of filling it 
with extreme accuracy; but when the veflel is judi.ioufly and 
neatly marked, the error of filling will, with due re, be 
exceedingly minute. By feveral repetitions of the fame ex- 
periments, Mr. Gilpin feemed to bring it within the T rhi'l> 
part of the whole weight. 

The above-mentioned confiderations induced me, as well as 
the gentlemen employed in the experiments, to give the pre- 
ference to weighing the fluid itfelf ; and that was accordingly 
the method praflifed both by Dr. Dollfuss and Mr. Gilpin 

in their operations. 

The veflel chofen as moft convenient for the purpofe was a 
hollow glafs ball, terminating in a neck of a 1 mall bore. That 
which Dr. Dollfuss ufed held 5800 grains ot diftilled water, 
but as our balance was fo extremely accurate, it was thought 
. expedient, upon Mr. Gilpin’s repetition of the experiments, 
to ufe one of only 2965 grains capacity, as admitting the heat 
of any fluid contained in it to be more nicely determined. The 
ball of this veflel, which may be called the weighing-bottle, 
meafured about 2,8 inches in diameter, and was fpherical, except 
a flight flattening on the part oppofite to the neck, winch ferved 
as a bottom for it to ftand upon. Its neck was formed of a 
portion of a barometer tube, ,25 of an inch in bore, and about 
if inch long; it was perfectly cylindrical, and on its outfide, 
very near the middle of its length, a fine circle or ring was cut 
round it with a diamond, as the mark to which it was to be 


1 


on Spirituous Liquors'. j2q 

filled with the liquor. This mark was made by fixing the 
bottle in a lathe, and turning it round with great care, in 
contact with the diamond. The glafs of this bottle was not 
very thick; it weighed 916 grains, and, with its filver cap, 
93 6 - ; 

When the fpecific gravity of any liquor was to be taken by 
means of this bottle, the liquor was firft brought nearly to the 
required temperature, and then the bottle was filled with it up 
to the beginning of the neck only, that there might be room for 
fhaking it. A very fine and fenfible thermometer (to be more 
particularly defcribed hereafter) Was then palled through the 
neck ot the bottle into the contained liquor, which fhewed 
v» nether it was above or below the intended temperature. In 
* ■ * ' former caie tne bottle was brought into colder air, or 0 ven 
plunged for a moment in cold water ; the thermometer in the 
mean time being frequently put into the contained liquor, till 
- 1 ** was found to fink to the right point. In like manner when 
tne liquor was too cold, the bottle was brought into warmer 
air, immerfed in warm water, or more commonly held be- 
tween the hands, till upon repeated trials with the thermome- 
ter the juft temperature was found. It will be underftood, that 
during the courfe of this heating or cooling, the bottle was 
very frequently fhaken between each immerfion of the ther- 
mometer ; and the top of the neck was kept covered, either 
with the finger, or a filver cap made on purpofe, as conftantly 
as poffible. Hot water was ufed to raife the temperature onlv 
in heats of 8o° and upwards, inferior heats being obtained by 
applying the hands to the bottle ; when the hot water was em- 
ployed, tne ball of the bottle was plunged into it and again 
quickly lifted out, with the neceliary fhaking interpofed, as 
Yql. LXXX. X. x often 


„- 0 Dr. Blagden’s Report , 

often as was neceffary for communicating the required heat to 
the liquor ; but care was taken to wipe the bottle dry after 
each immerfion, before it was lhaken, left any adhering 
moifture might by accident get into it. The liquor having by 
thefe means been brought to the defired temperature, the next 
operation was to fill up the bottle exactly to tae mark upon the 
neck, which was done with feme of the fame liquor, by means 
of a glafs funnel with a very fmall bore. Mr. Gilpin endea- 
voured to get that portion of the liquor which was employed 
for this purpofe, pretty nearly to the temperature of the liquor 
contained in the bottle; but as the whole quantity to be added 
never exceeded ten grains, a difference of ten degrees in the 
heat of that fmall quantity, which is more than it ever 
amounted to, would have occafioned an error of only of a 
degree in the temperature of the mafs. Enough of the liquor 
was put in, to fill the neck rather above the mark, and the 
fuperfluous quantity was then abforbed to great nicety, by 
bringing into contact with it the fine point of a fmall roll of 
blotting paper. As the furface of the liquor in the neck would 
be always concave, the bottom or centre of this concavity was 
the part made to coincide with the mark round the glafs : and 
in viewing it care was taken, that the near and oppofite fides of 
the mark Ihould appear exadlly in the fame line, by which 
means all parallax was avoided. A filver cap, which fitted 
tight, was then put upon the neck, to prevent evaporation ; 
and the whole apparatus was in that ftate laid in the fcale t)f 
the balance, to be weighed with all the exa&nefs poffible. 

The fpirit employed by Mr. Gilpin was furnilhed to him 

by Dr. Dollfuss, under whofe infpe&ion it had been re&fied 

from rum fupplied by Government. Its fpecific gravity, at 60 

* degrees 


on Spirituous Liquors. ^ 31 

degrees of heat, was ,82514. It was firft weighed pure, in 
the above-mentioned bottle, at every five degrees of heat, from 
30 to 100 inclufively. Then mixtures were formed of it and 


diftilled water, in every proportion from T '-th of the water to 
equal parts of water and fpirit ; the quantity of water added 
being fucceffively augmented, in the proportion of five grains to 
one hundred of the fpirit ; and thefe mixtures were alfo weighed 
in the bottle, like the pure fpirit, at every 5 degrees of heat. 
The numbers hence refulting are delivered in the following 
table ; where the firft column ftiews the degrees of heat ; the 
fecond gives the weight of the pure fpirit contained in the 
bottle at thofe different degrees ; the third gives the weight 
of a mixture in the proportions of 100 parts by weight 
of that fpirit to 5 of water, and fo on fucceffively till 
the water and the fpirit are in equal parts. The bottle 
itlelf, with its cap, having been previoufly counterpoifed, 
thefe numbers are the weights of the liquor contained in 
it, in grains and hundredths of a grain. They are the mean 
of three feveral experiments at leaft, as Mr. Gilpin always 
filled and weighed the bottle over again that number of times, 
if not oftener. The heat was taken at the even degree, as 
fhewn by the thermometer, without any allowance in the firft 
inftance, becaufe the coincidence of the mercury wfith a divi- 
fion can be perceived more accurately than any fraction can be 
eftimated ; and the errors of the thermometers, if any, it was 
fuppofed would be lefs upon the grand divifions of 5 degrees, 
than in any others. It mull be obferved, that Mr. Gilpin 
ufed the fame mixture throughout all _ the different tempera- 
tures, heating it up from 30° to ioo°; hence fome fmall error 

X x 2 in 


... Dr. Blagden’s Report 

fj j " 

in its ftrength may have been occafioned, in the higher degrees, 
by more fpirit evaporating than water ; but this, it is believed, 
rnuft have been trifling, and greater inconvenience would pro- 
bably have refultcd from interpofing a frefh mixture. 



/ 


\ 






/ 






TABLE 


i 


[To face p. 332 


TABLE L 


Weights at the different degrees of temperature. 


Heat. 

The pure 
fpirit. 

IOO grams 
of lpirit to 
5 grains, 
of water. 

IOO grains 
of fpirit to 
IQ grains 
of water. 

IOO grains 
of fpirit to 
1 5 grains 
of water. 

100 grains 
of fpirit to 
20 grains 
of water. 

100 grains 
of fpirit to 
25 grains 
of water. 

100 grains 
of fpirit to 
30 grains 
of water. 

100 grains 
of fpirit to 
35 grains 
of water. 

100 grains 
of fpirit to 
40 grains 
of water. 

1 00 grains 
of fpirit to 
45 grains 
of water. 

1 OO gi ains 
of fpirit to 
50 grains 
of water. 

3 ° 

35 

40 

45 

50 

55 

60 

65 

70 

75 

80 

85 

90 

95 

100 

Grains. 

2487,32 

2480,79 

2474 >» 8 

2467,52 

2460,77 

24 S 3.84 

2446,86 

2440,04 

2433.37 

2426,47 

2419,18 

2412,02 

2404,92 

2397.75 

2390,64 

Grains. 

2519.98 

2513.48 

2506.98 
2500,33 

2493.48 
2486,51 

2479,75 

2472,97 

2466,28 

2459,18 

2451,95 

2444,80 

2437,72 

2430,56 

2423,53 

Grains. 

2548.59 
2541,96 
2535,52 

2528,90 

2522,10 

2515,3° 

2508.60 
2501,87 
2495,00 
2488,03 
2480,83 
2473,68 
2466,64 
2459 , 5 1 
2452,63 

Grains. 

2573,86 

25 & 7,34 

2560,83 

2554,24 

2547.61 
2540,88 
2534,19 
2527,51 
2520,65 
2513,63 

2506.61 

2499.59 

2492.62 

2485,5! 

2478.59 

Grains. 

2596,65 

259°,15 

2583,70 

2577 ,l 6 

2570,64 

2 S 6 3,94 

2557,23 

2 S 5°-56 

2543>84 

2536,01 

2529,85 

2523,08 

2516,20 

25 ° 9 ,i 5 

2502,15 

Grains. 

2617,24 

2610,80 

2604.50 

2597,99 

259 ’, 5 ° 

2584,79 

2578,22 

2571,48 

2564,89 

2558,14 

2551,10 

2544,41 

2537,57 

2530.51 
2523,59 

Grains. 

2636,16 

2629,77 

2623,42 

2617,04 

2610,59 

2604.07 
2597,50 

2590.80 

2584,23 

2577,47 

2570,52 

2563.80 
2556>95 
2549,95 

2543.08 

Grains. 

2653,54 

2647.20 
2641,02 
2634,68 

2628.26 
2621,77 

2615.26 
2608,72 
2602,14 
2595,43 
2588,61 
2581,91 

2575.20 
2568,18 
2561,28 

Grains. 

2669,64 

2663,48 

2657,35 

2650,96 

2644,68 

2638,25 

2631,82 

2625,41 

2618,89 

2612,20 

2605,32 

2598,76 

2592,17 

2585,12 

2578,37 

Grains. 

2684,63 

2678,43 

2672,37 

2666,13 

2659,95 

2653,55 

2647,20 
2640,80 
2634,30 
2627,78 
2621,03 
2614,48 
2607.86 
2601, 12 

2594,45 

Grains. 
2698,4 1 
2692.32 
2686,37 
2680,25 
2674,04 
2667,72 
2661,45 
2655,09 
2648,65 
2642,17 

2635,47. 

2628,87 

2622,30 

2615,70 

2609,11 

Heat. 

O 

3 ° 

35 

40 

45 

5 ° 

55 

60 

65 

70 

75 

80 

85 

90 

95 

100 

1 00 grains 
of fpirit to 

55 g rains 

of water. 

100 grains 
of fpirit to 
60 grains 
of water. 

IOO grains 
of fpirit to 
65 grains 
of water. 

IOO grains 
of fpirit to 
70 grains 
of water. 

100 grains 
of fpirit to 
75 grains 
of water. 

too grains 
of fpirit to 
80 grains 
of water. 

IOO grains 
of fpirit to 
85 grains 
of water. 

100 grains 
of fpirit to 
90 grains 
of water. 

IOO grains 
of fpirit to 
95 grains 
of water. 

IOO grains 
of fpirit to 
IOO grains 
of water. 


Grains. 

2711.19 

2705.08 

2699.09 

2692.97 
2686,81 
2680,57 
2674,31 

2667.97 
2661,67 

2655.19 

2648,47 

2641,85 

2635,38 

2628,83 

2622,22 

Grains. 

2723.00 
2716,96 
271 1,02 
2704,82 
2698,63 
2692,44 
2686,16 

2680.00 

2673.68 
2667,32 

2660.69 
2654,19 
2647,61 
2641,10 
2634,38 

Grains. 

2733,84 

2727,78 

2721,90 

2715,98 

2709,92 

2703,67 

2697,44 

2691,22 

2685.02 
2678,60 

2672.02 
2665,54 
2659,07 
2652,56 
2 , 6 4 S >95 

Grains. 

2744,19 

2738,24 

2732,45 

2726,38 

2720,37 

2714,27 

2708,18 

2701,99 

2695,66 

2680,34 

2682,77 

2676,40 

2670,09 

2663,64 

2657,14 

Grains. 

2753, 6 7 

2747,90 

2742,18 

2736,21 

2730,27 

2724.20 
2718,26 
2712,06 
2705,87 
2699,57 
2693,03 
2686,77 

2680.60 

2674.20 

2667.61 

Grains. 

2762,61 

2756,97 

275 G 35 

2745.47 
2739,52 

2733.47 

2727.56 

2721.47 
2715,40 
2709,08 

2702.57 
2696,33 
2690,22 
2683,79 
2677,25 

Grains. 

2771,26 

2765-47 

2759,85 

2754,13 

2748.22 

2742.25 

2736.26 

2730.27 

2724.22 

2717,95 

2711,50 

2705,37 

2699,10 

2692,81 

2686,36 

Grains. 

2779,21 

2773,53 

2767.78 
2762,03 
27s6,2 5 

2750.32 

2744.32 
2738,35 
2732,42 
2726,25 

2719.78 
2713,69 

2707,44 

2701,18 

2694.76 

Grains. 

2786.47 

2780,75 

2775.15 

2769,55 

2763,67 

2757,82 

2751,87 

2745,93 

2740,00 

2733,92 

2727.49 

2721.47 

2715,22 

2708,91 

2702.50 

Grains. 

2797,26 

2787.59 
2782,06 
2776,40 
2770,62 
2764,72 

2758.82 

2752.82 
2746,88 

2740.83 

2734,49 

2728.60 
2722,32 
2716,04 
2700,75 


In 




eft Spirituous Liquors* 

In order to deduce the fpecific gravities from the numbers in 
the preceding table, it was neceffary to weigh diftilled water 
in the fame veffel. This Mr. Gilpin did, in the fame manner 
as before, at the different degrees of heat ; and the refult of 
his experiments is delivered in the following table, where the 
firft column fliews the heat, and the fecond gives the weight 
of the water, at that temperature, contained in the bottle. 


TABLE II. 

Weights and fpecific Gravities of diftilled Water. 


Heat. 

Weight of 
the 
water. 

| Specific gra 
I vity of the 
water. 

o 

30 

Grains. 


35 

2967,03 

1,00087 

40 

2967.34 

1,00091 

45 

2967,29 

1,00084 

50 

2966,97 

1,00066 

55 

2966,39 

1,00040 

60 

2965,39 

1,00000 

6 5 

2964,17 

599952 

,99896 

70 

2962,72 

75 

2961,03 

.99832 

80 

2959. 1 3 

,99762 

35 

2957.03 

,99685 

90 

2954,80 

• ,99602 

' 95 

2952,20 

.99507 

5 100 

2949,36 

.99404 


There 


Dr. Blagden’s Report 

3 There would be two methods of computing the fpecific gra- 
vity at the different temperatures, from thefe numbers; one, 
by taking the weight of the water, at the particular tempera- 
ture in queftion, for the ftandard; and the other by fixing on 
one certain temperature of the water, for mftance 6o°, to et e 
ftandard, with its bulffat which that of the fpmt at all dif- 
ferent degrees fhall be compared. I have preferred the latter 
method, though not the moll ufual, becaufe it (hews, more 

readily and fimply, the progreffion obferved in the changes of 

fpecific gravity, according to the heat and ftrengt 1 o vt 
mixture. This method, however, rendered it neceffary o 
make an allowance for the contraaion and expanfion of the 
bottle ufed for weighing the liquors, according to t ie ev iat J° n 
of their temperature from 6o°, either below, or a ove. o 
obtain this corredion, the expanfion of hollow gla s was ta en 
from General Roy’s experiments in the LXXVth volume o 
the Philofophical Tranfadions, as ,00005x7 of an inch upon 
a foot for every degree of heat, whence its effed, m enlarging 
the capacity of a fphere, was computed, and the refu .ting cor- 
redion added to the weight of the liquors in heats below 60 , 
and fubtraded from it in heats above. On the fame accoun a 

third column is given, in the preceding table, to rew t e pe 

cific gravity of water at the different temperatures, its weight 

at 6o° being taken as the ftandard. , 

Another corredion alfo became neceffary, on account o 
part of the ftem of the .thermometer which was not immeried 
in the liquor. This inftrument, made by Ramsden, had its 
ball ,22 of an inch in diameter, and its ftem 13 inc es in 
length. From the ball to the commencement of the fcale 13. 
inches of the ftem were bare, and then the fcale began, w^cn 


on Spirituous Liquors . ^35 

reached from 15 to no degrees. The part of it particularly 
made ufe of in theft experiments, namely, from 30° to ioo°, 
meafured 6,82 inches. The fcale was made of ivory, and ear- 
ned divifions to every fifth of a degree, the (quarters of which 
could be readily eftimated ; fo that the inftrument could be 
read off to twentieths of degrees. When the thermometer 
was immerfed in the weighing-bottle, the liquor reached up 
nearly to what would have been o° upon its ftem ; hence, as 
the heat of the room in which the experiments were made 
remained about 6o°, the corre&ion for the different heat of the 
quickfilver in the ftem from that in the ball of the thermome- 
ter was calculated according to Mr. Cavendish’s table, given 
in the LXVIIth volume of the Philofophica! Tranfa&ions. 
Thus the real heat of the fluid in the weighing-bottle being 
found, an allowance was made to reduce it to the exa£t degree 
indicated on the fcale of the thermometer. 

The precife fpecific gravity of the pure fpirit employed was 
,82514; but to avoid an inconvenient fra&ion it is taken, in 
conftru&ing the table of fpecific gravities, as ,825 only, a 
proportionable dedu&ion being made from all the other num- 
bers. Thus the following table gives the true fpecific gravity, 
at the different degrees of heat, of a pure re&ified fpirit, whofe 
fpecific gravity at 6o° is ,825, together with the fpecific gra- 
vities of different mixtures of it with water, at thofe different 
temperatures, as far as equal parts by weight* 


TABLE 


33 6 


Dr. Blagden’s Report 

table hi. 

Real fpecific gravities at the different temperatures, 


C2 


lioo grams! \ go graino iuu 
The pure lof fpirit to;of fpirit to of fpirit to 


fpirit. 


5 grams 
of water. 


, io grains ;i 5 grams 
lof water, 'of water. 


305,83899 ,85001 

35 .83673] ,84776 


,85967 


,86819 


40 ! 

451 


5 ° 


t * r * 

05 


60 

65 


83445 

,83215 

,82981 

,82741 

,82500 

,82262 


852861 


,84321 
,840841,85051 


701 ,82032 


>83843 ,84815 
,83609 ,84583 


8.33741^4350 


80 

.35 

90 

95 

IOO 


OS 

cu 


,81792 

,81543 

,81291 

,81044 

,80794 

,80548 


,83142 

',82896 

,82649 

,82396 


,82150 


,841 1 1 

,83869 

,83623 

,8337 


,81900 

,81657 


,831 


,849 


,82877 

,82639 


,8 


loo grains 100 grain 3 00 S ra ' ns 
of fpirit to of fpirit to|of Ipirit to 


55 grams 
of water. 


60 grains 65 grains 
of water, of water. 


,91454 

,91242 

,91034. 


,90822] 
,90608] 


>y_T — 

, 9 ° 39 °' 


60 ,901 ti 


1 Qi 


, 9 t8 53 

, 9 i6 44 

» 9 1 43 ^ 

,91222 

,91007 

,90791 

,90570 

,90359 

,90136 

,89916 


of 


65S ,89952', 

70 >89733 

75 , 89507 « 

SO ,892779 ^ . 
85 ,89043' ,89460' 
, 883 17: ,892 30 
,88 c88 ,89003 
•"3571,88769 


,92219 

,92009 

> 9 i8o 5 

> 9*599 

,91388 

,91170 

90954 

,90738 
9052. 
,90298 
90072 



,8961/ 

,89390! 

,89158) 


° 9 < 


(IOO grains! 100 grains 00 
of fpirit tojof fpirit to of fj 
20 grains! 25 grains 30 
of water, lof water, of 

1,87589 , 
,87363 , 

,87140 . 
D ,86913 . 
0 ,80688 

7 ,86455 
5 ,86223 

3 , 8 599 * 

5 ,85758 
1 ,855*7 

H ,85276 

13 ,85036 
1 ,84797 

J 3 , 84 S 5 0 

[ 3 ,8430b 

88284 ,8 
88061 ,8 
87843 ,8 
87617 ,8 

,87392 d 

,87159 ,s 
,86931 ,5 
,86698 ,i 
,86469 ,! 
,86234 ,' 

,85993 > 
, 8 57 S 7 
,855*8 , 
,85272 , 
,85031 , 

ins ioc grains] 
to of fpirit to 
11s 75 grains 
»r. of water. 

100 grains 1 
of fpirit to 0 
go grains <: 
of water. 0 

68 ,92888 

, 9 Z I 9 1 

62 ,92687 

5 9 2 995 

6l ,92489 

,92799 

5O ,92281 

,92595 

40 ,92075 

,92388 

;2S ,9186c 

,92176 

1 6 ,91656 

>9*97 * 

:oo ,9144c 

,9.769 

$80 ,9122- 

5 » 9 1 5 4 / 

>60 ,9100^ 

,91326 

13 > 9 ° 7 8( 

3 , 9 * l0 3 

?.o 9 ,9055* 

3 ,90882 

}8b ,9034 

2 ,90668 

7 0 3 qo 1 1 

,90443 

5301 ,8988* 

9 ,90215 


of fpirit to 

3 5 S raini 

of water 


,89509 


too grams 
of fpirit to 
40 grains 
of water. 


100 grams 
of fpirit to 

45 & rains 
of water. 


,89292 ,89839 
,890741 ,89626 


, 9 °° 53 , 9^558 

,90342 


100 gr is 
>f fpir :o 
50 gns 
of wai*. 


121 


water 


,93483 

93 2 


88855 
88632 
8 406 
88 1 b 1 

87954 

87725 

,8749! 

87258 

,87021 


,8940s 

,89187 

,88963 

,88740 


,88518 


,88291 

,88o S 8 

,87822 

,8759° 


,86787 ,87360 


,86542 

,86302 


; 00 grains 
of fpirit to 
90 grains 
of water. 


,87114 

,86879 


> 9 OI 3 

,89916 

,89701 

,89479 

,89259 

,89037 

,88810 

,88585 

,88352 

,88120 

,87889 

,87654 

,87421 


, 9 1C • 

,90! 1 

> 9 °§‘ 
> 9 °. • 
.90 ; 

,8c/;: 

,890 
,89 I 
,891, 

>894 
,88 V 
88 > 
, 88 ) 
, 88 ; 
,87' 


100 grains 
of fpirit to 
95 grains 
of water. 


8l 


92086 


,92887 

,92681 

,92472 

,92264 

> 9 20 55 

, 9 i8 45 
,91625' 
,91404 
.91 186 
,90967 

,90747 

,90522 


>9375 
,93553 
93353 
. 95 * 5-3 

,92952 

,92744 

, 9 2 53 6 

, 9 2 3 28 

,92121 

,91909 

,91683 

,9*465 

,91248 

> 9 I02 9 

,90805 


100 grains 
of fpirit to 
100 grains 
of water 


, 9399 6 

,93796 

,05602 

,93407 

,93202 
, 9 2 997 
, 9 2 79 
,92584 
,92377 

,92164 

,9*943 

,9*729 

, 9 * 5 * 

,9*290 

,91066 


,94225 

, 940 2 7 

, 93 8 35 

, 9363 8 


3436 


, 93 2 3 ' 


, 93 02 5 

,92816 

,92608 

,92397 

,92179 

,9*969 

, 9 * 75 * 

, 9 * 53 * 

, 9 * 3 *~ 


r ro 


on Spirituous Liquors* 



From this table, when the fpecific gravity of any fpirituous 
liquor is afcertained, it will be eafy to find the quantity of rectified 
fpirit, of the above-mentioned ftandard, contained in any given 
quantity of it, either by weight or meafure. As common arith- 
metic is competent to furnifh the rules for this purpofe, it 
would be fuperfluous to give them here. All the objedls of 
inquiry relative to this bufinefs (hould, I think, be reduced to 


Tables ; the firft of which might exhibit the fpecific gravities of 
different mixtures, from one to ioo parts of water, increafing 
by one, at every degree of heat from 40 to 80, being the utmoft 
limits of temperature that can be wanted in common pra&ice. 
This table need only be calculated to three places of figures* 
which will always give the quantity of fpirit true within a 
fiftieth part of the whole, and in the moft ufual degrees of heat 
within a hundredth ; and to this number of figures the areo- 
meter, or hydrometer, (hewing the fpecific gravities, could be 
fuited. A further reafon for continuing only to three places of 
figures is, that, accurate as Mr. Gilpin’s experiments have 
been,- fome irregularities are found in the two laft of the five 


decimals to which his tables are calculated. The greateft of 
thefe irregularities, I think, do not exceed the quantity cor- 
refponding to a difference of one-fifth of a degree of heat, and 
in general they are much lefs. A table might be conftru&ed 
to (hew what the numbers would probably have been, to the 
five places of decimals, if there had been no kind of error in 
the experiments. — -Another table (hould be of the volumes, ex- 
hibiting what proportion the fpirit and water bore to each other 
by meafure or bulk, in the different mixtures ; whence might 
be calculated a very ufeful table of Diminutions, to (hew 
when a given weight, or volume, of a certain fpirit and wa- 
Vol. LXXX. Y y tec 


g ' J)r. Blagden’s Report 

ter are mixed together, how much their bulk would be dimi- 
nifhed ; or, what is called by the dittillers the concentration. 
From fuch a table the diftiller could learn, what quantity of 
water he muft mix with fpirit of a given ftrength, m order to 
reduce it to proof fpirit, or any other ftrength ; and likewife 
what quantity of proof fpirit, or fpirit of any other ftrength, 
he may obtain, by adding water to fpirit of a given ftrength; 
both circumftances very neceffary to be known in the trade, 
and which feme of the Aiding rulers now in ufe proiefs to 


UUim. UUL. 

It may appear odd, that no mention has been made tul now 
of proof fpirit, the ftandard to which moft of the regulations of 
the excife have hitherto been referred. The reafons for not 
adopting this ftandard are : firft, that the ftrength of fpirit to 
be called proof is a mere arbitrary point, and by no means fo 
exactly determined as could be wiflied ; and, fecondly, that it 
feemed moft convenient to take for the ftandard the higheft 
ftrength of fpirit ufually found in commerce, and beyond 
which it cannot be rectified without a procefs of tome ex-, 
pence, fo that all the other degrees of ftrength might be 
reckoned one way, without the intervention of a middle point, 
inducing the neceflity of denominating fome above and otheis 
under. If, however, Government fhould find it expedient to 
pre-ferve the reference to proof ipirit, ■fiom th p tables given in 
this Report others may be conftruded, in which all the oid 
terms of over and under proof fhould be retained, and have a 
precife meaning, as foon as the ftrength to be called proof fliall 
x be finally fettled. By the A ft of 2 Geo. III. it is ordered, that 
the gallon of brandy or fpirits of the ftrength of one to fix 
under proof, ftiail be taken and reckoned at 7 lb. 130s., which 
is underftood by the trade to mean at 55’ of heat. Hence, 

& taking; 


on Spirituous Liquors* 

taking the weight of a gallon of water at the fame heat to be 
8 lb* 5,66 &c. 0%. *1 the fpecific gravity of this diluted fplrit will 
be found ,9335 at 6o° f ; whence, by a computation founded 
on the tables in this Report, the fpecific gravity of proof 
fpirit will come out ,916. But the rulers of correction be- 
longing to Dioas’s and Quin’s hydrometers give the fpecific 
gravity of proof fpirits about ,922 at 55°, equivalent to ,920 at 
6oh The former, ,916, correfponds to a mixture of 100 parts 
of fpirit with 62 by meafure, or 75 by weight, of water; and 
the latter, ,920, to a mixture of loo parts of fpirit and 66 by 
meafure, or 80 by weight, of water. The difference is con- 
fiderable; but the firft is undoubtedly moft conformable to the 
exifting Ads of Parliament. If, therefore, it be thought right 
to preferve the term proof-fpirit in our Excife Laws, it may 
be underftood to mean fpirit, whofe fpecific gravity is ,916, 
and which is compofed of 100 parts of redified fpirit at ,82c. 
and 62 parts of water by meafure, or 75 by weight ; the whole 
at 60 degrees of heat. 


I have chofen this point of the thermometer, 6o°, in pre- 
ference to 55°, becaufe it Is much the moft fuitable for experi- 
ments, being the temperature at which a room feels pleafant, 
and in which any operation, however flow and tedious, can be 
executed without the uneafy fenfation of cold : for this reafon 
it has been adopted by many Englifh philofophers. In the 
table formerly recommended, from 40 to 80 degrees of the 
thermometer, it will be the middle temperature. 


* Probably 8 lb . 5,^2 oz. is nearer* 

f This fpecific gravity indicates a mixture of 107 grains of water with 100 
of fpirit, and confequently is below Mr. Gilpin’s prefent Tables, which go only 
to equal parts. 


y 


The 


240 Dr. BlAgden’s Report 

The fpecific gravity of ,825 having been fixed upon as the 
ftandard of re&ified fpirit in our tables, Mr. Gilpin was de- 
fired to afcertain by experiment what proportion of water 
would be neceflary, to reduce the lighteft alcohol in his poffef- 
fion to that ftandard. This was home alcohol, already men- 
tioned, which Mr. Lewis had furnilhed; and its fpecific gra- 
vity being ,814196 at 6o°, 3000 grains of it mixed with 135 
grains of diftilled water formed a compound, whofe fpecihc 


gravity was ,825153 ; that is, in round numbers, 100 grains 
of alcohol at ,814 with 4,5 grains of water, form our ftandard 
of fpirit at ,825. 

Perhaps fome perfons may object to the preceding experi- 
ments, on account of the fmall quantities mixed and weighed. 
Undoubtedly experiments on a large fcale have fome advan- 
tages ; but thefe in general depend more on the coarlenefs of 
tools, and clumfinefs of operators, than on the nature of the 
operations. If inftruments be exceedingly exa<ft, and the ex- 
perimenter equal to the talk of ufing them properly, I believe 
the errors upon moderate quantities will be quite as fmall in 
proportion as upon large; and in this particular inftance, where 
the greateft fource of error lay in the determination of the 
heat, the fmaller quantities had in that refpefl an evident 
advantage, it being much eafier to bring fix ounces of a liquor 
to an uniform temperature than fo many gallons. One of our 
moft eflential inftruments, namely, the balance, was fo much 
fuperior in nicety to any thing that could be wanted in thefe 
experiments, that error in weighing muft be thrown entirely 
out of the queftion. It was conftrudled by Mr. Ramsden * 
and fome account, though very imperfeft, of its admirable 
mechanifm, as well as of its extreme fenfibility, even when 


on Spirituous Liquors . 

loaded with confiderable weights, has been given in the XXXlIId 
volume of the Journal de Pbyjique. 

I muft not conclude this part of the Report without ob- 
ferving, that as the experiments were made with pure ipirk 
and water, if any extraneous fubftances are contained in the 
liquor to be tried, the fpeciiic gravity in the tables will not 
give exactly the proportions of water and fpirit in it. The 
fubftances likely to be found in fpirituous liquors, where no 
fraud is fufpedted, are, eflential oils, lb me times empyreumatic, 
mucilaginous or extradlive matter, and perhaps fome faccha- 
rine matter. The efFedt of thefe, in the courfe of trade, 
feems to be hardly fuch as would be worth the cognizance of 
the excile, nor could it ealily be reduced to any certain rules. 
Eflential and empyreumatic oils are nearly of the fame fpecific 
gravity as fpirit, in general rather lighter, and therefore, not- 
withftanding the mutual penetration, will probably make little 
change in the fpecific gravity of any fpirituous liquor in which 
they are difloived. The other fubftances are all heavier than 
fpirit; the fpecific gravity of common gum being 1,482* 
and of fugar 1,606, according to the tables of M. Brisson. 
The effedt of them therefore will be to make fpirituous liquors 
appear lefs ftrong than they really are. An idea was once en- 
tertained of endeavouring to determine this matter with fome 
preciflon; and accordingly Dr. Dollfuss evaporated 1000 
grains of brandy, and the fame quantity of rum, to drynefs ; 
the former left a reliduum of 40 grains, the latter only of 8 f 
grains. The 40 grains of refiduumfrom the brandy, difloived 
again in a mixture of 100 of fpirit with 50 of water, in- 
creafed its fpecific gravity ,00041 ; hence the effedl of this 
extraneous matter upon the fpecific gravity of the brandy con- 
taining it would be to increafe the fifth decimal by 6 nearly, 

equal 


Dr. Blagden’s Report 

eoual to what would indicate, in the above-mentioned mixture, 
about one-feventh of a grain of water more than the truth, to 
100 of fpirit : a quantity much too minute for the confideration 

of Government. 


part II. 

* 

On Hydrometers. 

THE readied way of afcertaining fpecific gravities, and un- 
doubtedly the mod convenient for public bufinefs, is by hy- 
drometers ; and, I conceive, thofe of the fimpled conduc- 
tion to be bed upon the whole, efpecially if more accurate 
means are kept at hand, to be reforted to in cafe of difputes. 
An hydrometer of glafs would be the mod certain ; but whether 
it be of that fubdance, or of metal, it diould confid of a ball, 
or rather bulb, fo poifed as that a certain part diould be always 
downmod in the liquor, and having a dem rifing from it on 
the oppodte part, which would confequently keep upright in 
ufing the indrument. On the fize of this dem, the fenlibility 
of the hydrometer chiefly depends. In the old areometers the 
dem was made fo large, that the volume of water difplaced 
between its lead and greated immerfions was equal to the 
whole difference of fpecific gravity between water and alcohol, 
or perhaps more ; whence its dale of divifions mud be veiy 
fmall, and could not give the fpecific gravity with much accu- 
racy. To remedy this defed, weights were introduced, by 
means of which the dem could be made fmaller, each weight 
affording a new commencement of its fcale ; fo that the fize of 
the divifions on a given length of dem was doubled, tripled, 
\ - quadrupled^ 


on Spirituous Liquors * 

quadrupled, &c. according as one, two, three, or more weights 
were employed, the diameter of the item being leffened in the 
fubduplicate proportion of the increafed length of the divi- 
fions. Of late this principle feems to have been carried to ex- 
cefs;, the number of weights adapted to fome hydrometers 
being fo great as to prove very inconvenient in practice. A. 
mean between the two methods would certainly be bell, which 
might be fuited to our tables in the following manner. 

It is propofed to determine the fpecific gravity to three places- 
of decimals, water being taken as unity : the whole compafs 
of numbers, therefore, from rectified fpirit to water, at 60 
degrees of heat, would be the difference between ,825 and 
1,000, that is, 175 ; call it 220 to include the lighted: fpirit 
and heavieft water, at all the common temperatures. Of thefe 
divifions the ftem might give every twenty, and then ten 
weights would be diffident for the whole 220. By making v 
the ftem carry twenty divifions, an inconvenience much com- 
plained of, that of fluffing the weights, would in great rpiea- 
iure be avoided ; becaufe a per foil converfant in fuch- bufinefs 
would feldom err to that extent in judging of the ftrength of* 
his fpirit previous to trial ; and yet the ftem would' not need to- 
be fo large, or the divifions fb fmall, as to preclude the defired 
accuracy. In conformity to this arrangement it would be pro- 
per, that the weights adapted to the hydrometer fhould be 
marked -with the numbers of the fpecific gravity, zero on the top- 
of its ftem,. without a weight, being fuppofed to mean Soo 7 
and 20 at the bottom of the ftem to fignify 820, which number 
the firft weight would carry ; the fucceffive weights would be 
marked 840, 860, &c. ; and the divifion on the ftem cut by 
the fluid under trial would be a number to be always added to 
the number marked upon the weight,- the fum of the two 

fhewing. 


Dr* Blagden’s Report 

fhewing the true fpecific gravity. The weights (hould uu- 
queftionably be made to apply on the top of the item, fo as 
never to come into contact with the liquor ; and in ufing the 
hydrometer its ftem fhould always be prefled down lower 
than the point at which it will ultimately reft, that bv being 
wetted it may occafion no refiftance to the fluid. The inftru- 
ment itfelf fhould be of as regular a fliape, and with as few 
inequalities and protuberances, as poffible, that all unneceflary 
obftruftion to its motions may be avoided. 

As it is not probable but difputes will fometimes arife, I 
think it would be advifable, that fome of the principal excife 
offices fhould be provided with a good pair of fcales, and a 
weighing-bottle properly marked, the quantity of whole con- 
tents of diftiiled water at 6o° had been previoufly determined. 
By filling this bottle up to the mark with the f pirit in quef- 
tion, and dividing its increafe of weight by the given weight 
of water required to fill it, the fpecific gravity of the fpirit 
would, I think, be better afcertained, even under the manage- 
ment of a common operator, than by the moft dexterous ufe of 
the hydrometer. 

The fimpleft and moft equitable method of levying the duty 
on fpirituous liquors would be, to confider rectified fpirit as the 
true and only excifable matter. On this principle, all fuch 
liquors would pay exadtly according to the quantity of re£ti- 
fied fpirit they contain ; fo that when a cafk, for inftance, of 
any fpirits was prefented to the revenue officer, his bufinefs 
would be to determine from the quantity, fpecific gravity, and 
temperature, of the liquor, how many gallons, or pounds, of 
re&ified fpirit enter into its compofition ; each of which gal- 
lons, or pounds, ffiould be charged a certain fum. The com- 
plicated regulations attending the adaption of the duties to 

different 


on Spirituous Liquors, 345 

different decrees of fcrength would thus he avoided ; and it is 
believed, that many frauds might he prevented, which artful 
perfons have now an opportunity of praftifing, by altering the 
*ffrength of their fpirit in a variety of ways. From the tables 
already recommended, it would be eafy to deduce th is quantity 
cf reftified fpirit, either by weight or meafure, in any given 
quantity of a fpirituous liquor ; or other tables might be con- 
firufted which fhould (hew it at once by infpeftion. 1 

If, however, it be thought by Government moil expedient 
not to make any eflentiaT change in the prefect' manner of col- 
lefting this article of the revenue, I would at leaft recommend, 
that the fpecific gravity fhould be fubftituted for the relation to 
proof fpirit. Thus, inftead of ordering fo much duty per 
gallon to be- paid by fpirits one to fix under proof, it may be 
enafted, that the fame fum fhall be paid by fpirit of ,9355 
fpecific gravity, or, not to be too precife, by fpirit from ,930 
to ,935, and fo on for any other degrees of ftrength ; a certain 
temperature, fuppofe 6o°, being always underftood to be meant 
when fpecific gravity is mentioned in an Aft of Parliament. 

The duties to be laid according to either of thefe methods 
may readily be adjufted or equalized to thofe paid at prefent, as 
far as the latter can be determined from the Aft of 2 "George 
III. referred to above, or by any of the inftruments now In ufe. 

It will give me very fincere pleafure if the preceding experi- 
ment and remarks fhould tend to advance the profperity of this 
country, by introducing a more juft and advantageous mode of 
colleftion into fo material a branch of the revenue. 

Z z 


Vol. LXXX. 


[ 346 J 


XIX. Obfervations on the Sugar Ants . In a Letter from John 
Cadies, E fcj. to Lieut . Gen . Melvill, F, R . 


Read May 22, 1790. 

T HE Sugar Ants, fo called from their ruinous effects on 
the lugar-cane, fird made their appearance in Grenada 
about twenty years ago on a fugar plantation at Petit Havre, 
a Bay five or fix miles from the town of St. George, the 
capital, conveniently fituated for fmuggling from Martinique. 
It was therefore concluded, they were brought from thence in 
feme vefi'el employed in that trade ; which is very probable, as 
colonies of them in like manner were afterwards propagated in 
different parts of the ifland by droghers, or veflels employed in 
carrying dores, &c. from one part of the ifland to another. 

From thence they continued to extend themfelves on all 
Tides, for feveral years ; dedroying in fucceflion every lugar 
plantation between St. George’s and St. John’s, a lpace of 
about twelve miles. At the fame time, colonies of them 
began to be obferved in different parts of the ifland, particularly 
at Duquefne on the north, and Calavini on the fouth fide 
of it. 

All attempts of the planters to put a dop to the ravages of 
thefe infeCts having been found ineffectual, it well became the 
leg if! at ure to offer great public rewards to any who fhould dis- 
cover a practicable method of dedroying them, fo as to permit 
the cultivation of the fugar- cane as formerly. Accordingly, 


/ 


Mr. Castles’s Obfervations , &c. 34 y 

an Adt was paffed, by which fuch difeoverer was entitled to 
twenty thoufand pounds, to be paid from the public treafury of 
the ifland. 

Many were the candidates on this occafion, but very far 
were any of them from having any juft claim: neverthelefs, 
confiderable fums of money were granted, in confideration of 
trouble and expences in making experiments. 

In Grenada there had always been feveral fpecies of ants, 
differing in fize, colour, &c. which however were perfedtly 
innocent with refpedt to the fugar-cane. The ants in queftion, 
on the contrary, were not only highly injurious to it, but to 
feveral forts of trees, fuch as the lime, lemon, orange, &c. 

Thefe ants are of the middle fize, of a (lender make, of a 
dark red colour, and remarkable for the quicknefs of their 
motions ; but their greateft peculiarities were, their tafte when 
applied to the tongue, the immenfity of their number, and 
their choice of places for their nefts. 

All the other fpecies of ants in Grenada have a bitter mufky 
tafte. Thefe, on the contrary, are acid in the higheft degree, 
and, when a number of them were rubbed together between 
the palms of the hands, they emitted a ftrong vitriolic ful- 
phureous fmell ; fo much fo, that, when this experiment was 
made, a gentleman conceived, that it might be owing to this 
quality that thefe infedts were fo unfriendly to vegetation. This 
criterion to diftinguilh them was infallible, and known to every 
one. 

Their numbers were incredible. I have feen the roads 
coloured by them for miles together ; and fo crowded were they 
in many places, that the print of the horfes feet would appear 
for a moment or two, till filled up by the furrounding multi- 
tude. This is no exaggeration. All the other fpecies of ants, 

Z z z although 


24.8 Mr. Castles’s Obfer various on 

although numerous, were circumfcribed and confined to a 
fmall fpot, in proportion to the fpace occupied by the cane 
ants-, as a mole hill to a mountain. 

The common black ants of that country had their nefts 
about the foundation of houfes or old walls; others in hollow 
trees ; and a large fpecies, in the patiures, defcending by a fmall 
aperture under ground. The fugar ants, I believe, univerfally 
conftruded their nefts among the roots of particular plants and 
trees, fuch as the fugar-cane, lime, lemon, and orange trees, 
&c. 

The deftr udion of thefe ants was attempted chiefly two 
ways ; by poifon and the application of fire. 

For the firft purpofe arfenic and corrofive fublimate, mixed 
with animal fu.bftances, fuch as fait fifh, herrings, crabs, and 
other (hell- fifh, &c, were ufed, which was greedily devoured 
by them. Myriads pf them were thus deftroyed ; and the 
more fo, as it was obferved by a magnifying glafs, and indeed 
(though not fo diftindlly) by the naked eye, that corrofive 
fublimate had the effed of rendering them fo outrageous that 
they deftroyed each other ; and that effect was produced even by 
coming into contact with it. But it is clear, and it was found, 
that thefe poifons could not be laid in fufficient quantities over 
fo large a trad of land, as to give the hundred-thoufandth part 
of them a tafte, and confequently they proved inadequate to 
the talk. 

The ufe of fire afforded a greater probability of fuccefs ; for 
(from whatever caufe) it was obferved, that if wood, burnt to 
the ftate of charcoal, without flame, and immediately taken 
from the fire, was laid in their way, they crowded to it in fuch 
amazing numbers as foon to extinguifh it, although with the 
deftrudion of thoufands of them in effecting it. This part of 

their 


( 


the Sugar Ants . 


349 


their hi (lory appears fcarcely credible; but, on makinS the 
experiment myfelf, I found it literally true. 1 laid fire, as 
above defcribed, where there appeared but a very few ants, and 
in the courfe of a few minutes thoufands were feen crowding 
to it and upon it, till it was perfectly covered by their dead 
bodies. Holes were therefore dug at proper diftances in a cane 
piece, and fire made in each of them. Prodigious quantities 
perifhed in this way ; for thofe fires, when extinguished, ap- 
peared in the Shape of mole hills, from the numbers of their 
dead bodies heaped on them. Neverthelefs they foon appeared 
again as numerous as ever. This may be accounted for, not only 
from their amazing fecundity, but that probably none of the 
breeding ants, or young brood, buffered from the experiment. 

For the fame reafon, the momentary general application of 
fire by burning the cane trafti (or draw of the cane) as it lay 
on the ground, proved as little effectual ; for although, perhaps, 
multitudes of ants might have been deftroyed, yet in general 
they would efcape by retiring to their nefts under cover, and 
out of its reach, and the breeding ants, with their young 
progeny, muff have remained unhurt. 

Mr. Smeathman (who wrote a Paper on the Termites, or 
W hite Ants, of Africa, and was at Grenada at this time) 
imagined, that thefe ants were not the caufe of the injury 
done to the canes. Pie fuppofed, it was owing to the blaft:, a 
difeafe the canes are fubject to, faid to arife from a fpecies of 
fmall flies, generated on their Stems and leaves ; and that the 
ants were attracted in Such multitudes merely to feed on them. 

There is no doubt, that where this blaft exifted it conftituted 
part of the food of the ants : but this theory was overthrown, 
by obferving, that by far the greateft part of the injured 
canes had no appearance of that fort, but became ftckiy and 

withered, 


35 ° 


Mr. Castles’s Obfervciliom on 


withered, apparently for want of nourilhment. Befides, had 
that been the cafe, the canes muft have been benefited inftead 

of being hurt by thefe infe&s. 

For the cure of the blaft, he propofed the application of 
train oil, which had not the leaf!: effect in preventing the mil- 
chief, and, if it had, could never have been generally enough 
ufed to anfwer the purpofe. 

This calamity, which relifted fo long the efforts of the 
planters, was at length removed by another, which, however 
ruinous to the other iflands in the Weft Indies, and in other 
refpeds, was to Grenada a very great bleffing, namely, the hur- 
ricane in 1780 ; without which it is probable the cultivation of 
the fugar-cane in the molt valuable parts of that iflauu mult me e 
in a great meafure been thrown afide, at leaft for lome yeaio. 
How this hurricane produced this effect has been conlxJered 
rather as a matter of wonder and furprize than attempted to 
be explained. By attending to the following obfervations, tne 


difficulty I believe will be removed. 

Thefe ants make their nefts, or cells for the reception of 

their eggs, only under or among the roots of luch trees or 

plants as are not only capable of protecting them from heavy 

rains, but are at the fame time fo firm in the ground as to afford 

a fecure bafis to fupport them againft any injury occafioned by 

the agitation of the ufual winds. This double qualification the 

fugar-cane poffeffes in a very great degree ; for a ftool of canes 

(which is the affemblage of its numerous roots where the Items 

begin to Ihcot out) is almoft impenetrable to rain, and is alio, 

from the amazing numbers and extenfion of the roots, firmly 

fixed to the ground. Thus, when every other part of the field 

is drenched with rain, the ground under thofe ftools will be 

found quite dry, as I and every other planter muft have 

obferved 


l 


the Sugar Ants. ^51 

obferved when digging out the fiools in a cane piece, to pre- 
pare for replanting. And when canes are lodged or laid down 
by the ufual winds, or from their own luxuriancy, the ftools 
commonly remain in the ground ; hence, in ordinary weather, 
their nefts are in a ftate of perfeft fecurity. 

The lime, lemon, orange, and fome other trees, afford thefe 
infers the fame advantages, from the great number and quality 
of their roots, which are firmly fixed to the earth, and are very 
laige , oefides which, their tops are fo very thick and umbrageous 
as to prevent even a very heavy rain from reaching the ground 
underneath. 

Oa the contrary, thefe ants nefts are never found at the roots 

of trees or plants incapable of affording the above prote&ion : 

luch, for in fiance, is the coffee*tree. It is indeed fufficiently 

firm in the ground, but it has only one large tap root, which 

goes ftraight downwards, and its lateral roots are fo fmall as to 

afford no flicker againft rain. So again, the roots of the cotton 

fiirub run too near the furface of the earth to prevent the accefs 

of rain, and are neither fufficiently permanent, nor firm 

enough to refill the agitation by the ufual winds. The fame 

obfervatson will be found true with refpedt to cocao, plantains, 

maize, tobacco, indigo, and many other fpecies of trees and 
plants. 

Tiees or plants of the firft defcription always fuffer more or 
lefs in lands iufefted with thefe ants ; whereas thofe of the 
latter never do. Hence we may fairly conclude, that the mif- 
cmef done by thefe infedts is occafioned only by their lodging 
and making their nefts about the roots of particular trees or 
plants. Thus the roots of the fugar-canes are fomehow or 
other to much injured by them, as to be incapable of perform- 
ing their office of Applying due nourifhment to the plants, 

which 


o;2 

D ~ 


Mr. Castles’s Ob/ervations on 

which therefore become (ickly and {tinted, and confequerrt f I 
do not afford juices fit for making fugar in either tolerable 

quantity or quality. 

That thefe ants do not feed on any part of the canes or trees 
affected feems very clear, for no lots of 1ubtbr.ee in either me 
one or the other has ever been obferved ; nor have they ever 
been feen carrying off vegetable fubftarc s of any fort. Ins 
truth of this will farther appear by the following fact. 

A very fine lime-tree, in the pad u re of Mount William 
eftate, at a confiderable dhbn.ee from any canes, but near the 
dwelling boufe, had fickened and died loon after the ants made 
tlmir^appearance on that effate. After ^ had remained in - 
ftate, without a Angle leaf, or the lead verdure, for kve.a. 
months, on examination, a very few ants appeared about it 5 but 
when with the manager’s permiffion it was grabbed out, a 
aftonifhing quantity of ants and tots ’nefts, full of eggs, were 
found about its roots, all of which were quite dead, and many j 

of them rotten. „ 

That this tree conflituted no part of their food is quite 

certain ; but, while it continued to afford them, proper lecunty 
, for their nefts, they ftill continued their abode. 

On the contrary, there is the greateft preemption tnat thele 
ants are carnivorous, and feed entirely on animal fubftances ; 
for if a dead infeft, or animal food of any iort, was laid in 
their wav, it was immediately carried off. It was found almoft 
impoffible to preferve cold viftuals from them. The largeit 
carcaffes, as foon as they began to become putrid, fo as that they 
could feparate the parts, foon difappeared. Negroes witn fores 
had difficulty to keep the ants from the edges of them. bey 

deftroyed all other vermin, rats in particular, fo. w^a t^y 
cleared every -plantation they came upon, which they prooaoly 


.. . the Sugar Ants, 

effected by attacking their young. It was found that poultry, 
or other fmall flock, could be raifed with the greateft difficulty ; 
and the e}^es, nofe, and other emunctories of the bodies of 
dying or dead animals were inftantly covered with them. 

In the year 1780, many of the fugar eftates which had been 
firft infefted with thefe ants had been either abandoned, or 
p,ut into other kinds of produce, principally cotton ; which, as 
I have above obferved, do not afford conveniency for their 
qefts. In confequence, the ants had there lo much decreafed 
in number, that the cultivation of fugar had again begun to be 
re-affumed. But it was very different in thofe plantations 
which had but lately been attacked, and were ftill in fugar. 
At Duquefne, particularly, at that time they were pernicious 
in the higheft degree, fp reading themfelves on all fides with 
great rapidity, when a hidden flop was put to their progrefs 
by the hurricane which happened near the middle of October 
that year. How this was effected, I think, may be explained 
by attending to the above obfervations. 

From what has been faid it appears, that a dry fituation, fo 
as to exclude the ordinary rains from their nefts or cells, appro-* 
priated for the reception of their eggs or young brood, is abfo- 
lutely neceflary ; but that thefe fltuations, however well calcu- 
lated for the ufual weather, could not afford this protection 
from rain during the hurricane, may be eafily conceived. 

When by the violence of the tempeft heavy pieces of artil- 
lery were removed from their places, and houles and fugar- 
works levelled, with the ground, there can be no doubt that 
trees and every thing growing above ground muft have grea li y 
fuffered. This was the cafe. Great numbers of trees and 
plants (which ref ft commonly the ordinary winds) were torn 
out by the root. The canes were univerfally either lodged or 
Vol. LXXX. A a a twilled 


Air. Castles’s Observations on 

twilled about as if by a whirlwind, or torn out of the ground 
altogether. In the latter cafe, the breeding ants, with their 
progeny, mult have been expofed to inevitable deftrudtion from 
the deluge of rain which fell at the fame time. The number 
of canes, however, thus torn out of the ground, could not 
have been adequate to the fudden diminution of the fugar 
ants; but it is eafy to conceive, that the roots of canes which 
remained on the ground, and the earth about them, were fo 
agitated and lhaken, and at the fame time the ants nefts were fo 
broken open, or injured, by the violence of the wind, as to 
admit the torrents of rain accompanying it. I apprehend, 
therefore, that the principal deftrudtion of thefe ants muff 
have been thus effedted. 

Two circumftances tended to facilitate this happy effedt. 
Many of the roots of the canes infedted, as above obferved, 
were either dead or rotten, fo as not to be capable of making 
the fame refiftance to the wind as thofe in perfedt health. And 
this hurricane happened fo very late as the month of Odtober, 
when the canes are always fo high above ground as to give the 
wind fufficient hold of them, which at an earlier period would 

not have been the cafe. 

That many of the cane ants were fwept off by the torrents 
of rain into the rivers and ravines, and thus periAed, I have 
no doubt ; but if we confider the obftacles to this being very 
general, it could have had but fmall effedt in conliderably re- 
ducing their numbers ; for on flat land it could not have hap- 
pened. In hanging or hilly land, the cane tralh would afford 
great Ihelter, and the ants would naturally retire to their nefts 

for fecurity, when they found their danger. 

Some have fuppofed, that the fugar ants, after a certain 

time, degenerate, and become inoffenfive ; and in proof of this, 
° • they 


the Sugar Anfu 355 

they fay, Martinique and Barbadoes were freed from their bad 
effedts without a hurricane or any other apparent caufe. 

The idea of any fuch extraordinary and unheard-of devia- 
tion of nature is too contemptible to deferve an anfwer ; but 
the reafon is obvious. The planters there either abandoned 
their cane lands, or planted them in coffee, cocao, cotton, in^ 
digo, &c. none of which, according to the above obfervations, 
afford the ants proper conveniency for the propagation of their 
fpecies; and therefore their numbers rauft have fo much decreafed 
as to re-admit the culture of the fugar-cane as before. At the 
fame time it is very probable, that this diminution might have in 
part been owing to fomething of the hurricane kind ; for it is 
well known, that ftrong fqualls of wind, attended with heavy 
rains, are frequent in the Weft Indies, although they do not 
laft fo long, nor are fo violent, as to deferve the name of a 
hurricane. 

It mu ft not however be denied, that though nature, for a 
time, may permit a particular fpecies of animal to become fb 
unproportionabiy numerous as to endanger fome other parts of 
her works, (he herfelf will in due time put a check upon the 
too great increafe ; and that is often done by an increafe of 
fome other animal inimical to the former deftroyers. In the 
prefent cafe, however, nothing of that fort appeared ; there- 
fore, when a plain natural caufe, obvious to our fenfes, 
occurred, by which we can account for the amazing and fudden 
decreafe of thofe ruinous infedts, it is unneceffary to recur to 
other poffible caufes, too minute for our inveftigation. 

All I have faid on this fubjedt would certainly be of little or 
no confequence, did it not lead to the true method of culti- 
vating the fugar-cane on lands infefted with thofe deftrudtive 

A a a z infe&s ; 


2^6 Mr . Castles's Obfervatlons on 

infers ; in which point of view, however, it becomes 

important. 

If then the above dodlrine be juft, it follows, that the whole 
of our attention muft be turned to the deftrudion ot the nefts 
of thefe ants, and confequently the breeding ants with their 
eggs or young brood. 

In order to effed this, all trees * and fences, under the roots 
of which thefe ants commonlv take their refidence, fhould firft 
be grubbed out ; particularly lime fences, which are very com- 
mon in Grenada, and which generally buffered from the ants 
before the canes appeared in the leaft injured. After which 
the canes fhould be flumped out with care, and the ftools 
burnt as foon as pofiible, together with the field trafh (or the 
dried leaves and tops of the canes), in order to prevent the 
ants from making their efcape to new quarters. The beft way 
of doing this, I apprehend, will be, to gather the field trafh 
together in confiderable heaps, and to throw the ftools as foon 
as dug out of the ground into them, and immediately apply 
fire. By this means multitudes muft be deftroyed ; for the 
field trafh, when dry, burns with great rapidity. The kind 
fhould then be ploughed or hoe-ploughed twice (but at leaft 
once) in the wetteft feafon of the year, in order to admit the 
rains, before it is hoed for planting the cane : by thefe means 
thefe mfedts, I apprehend, will be fo much reduced in num- 
ber as at leaft to fecure a good plant cane. 

But it is the cnftom in moft or the vV eft India iflands to 
permit the canes to rattoon ; that is, after the canes have once 
been cut down, for the purpofe of making Tugar, they are 

* Particular fruit trees may probably be preferved, without detriment, by 
carefully removing the earth from about their foots, deftroying the ants netfs, 
and afterwards replacing either the fame or new earth* 


fuffered 


the Sugar Ants . ^57 

fuffered to grow up again, without replanting; and this gene- 
rally for three or four years, but fometimes for ten, fifteen, or 
twenty. In this mode of culture the {tools become larger 
every year, fo as to grow out of the ground to a confiderable 
height, and by that means afford more and more Oielter to the 
ants nefts ; therefore, for two or three fucceffive crops, the 
canes fhould be replanted yearly, fo as not only to afford as 
little cover as poffibie for the ants nefts, but continually to 
difturb fuch ants as may have efcaped, in the bufinefs of pro- 
pagating their fpecies. 

That confiderable expence and labour will attend putting 
this method into execution, there is no doubt. An expenfive 
cure, however, is better than none ; but from the general 
principles of agriculture, I am of opinion, that the planter 
will be amply repaid for his trouble, by the goodnefs of his 
crops, in confequence of the fuperior tilth the land will receive 
in the propoied method. Of this we have a proof in the 
ifland of St. Kitt’s, where they conftantly replant their canes 
yearly: and it is very well known, that an acremf cane land 
there gives a greater return than the fame quantity in any other 
ifland. In St Kitt’s, five hogfheads per acre is common yield- 
ing in good land. In Grenada, from two to three hogfheads 
from plant canes, and half that quantity from rattoons. Thus^ 
although the St. Kitt’s planter cuts only one half of his cane land 
yearly, in a given number of years he makes a greater revenue 
than the Grenada planter on the p refen t mode of rattooning ? 
when four-fifths of the cane land is yearly cut 

Some may be of opinion, that it would be more advan- 
tageous to change the produce than to purfue the propofed 
method ; on which I (hall only obierve, that it appears to 
me, that one half of the ufual crop of fugar, thus produced, 

will 


2 Mr. Castles’s Obfervations, &c. 

will be more advantageous to the planter (when at the fame time 
progrefs is making in deftroying the fugar ants) than a full 
crop of any other produce. In feme very few fixations cot- 
ton perhaps may be excepted. As to coffee, it is to be con i- 
dered that it gives no return till the third year after planting, 
and not a full crop till the fifth. Cocao begins to bear in five 
years ; but yields little till the feventh : and indigo not only 
exceedingly impoverifhes the land, but is unhealthy to the 
negroes. Add to this, that far the greateft part of fugar lands 

are unfit for the culture of any of thefe. 

It would carry this Letter to too great a length were I to 
adduce all that may be faid on this fubjed ; I fhall therefore 
conclude by obferving, that the beft proof of the truth of the 
above dodrine will be the fuccefs attending the propofed me- 
thod of cultivation, or one of the fame tendency, vm. to 
attempt the deftrudion of the nefts of thefe infeds, and con- 
fequently the breeding ants, with their young broods; for 
their fecundity appears to be fo prodigioufly great as to render 
it altogether impoffible to deftroy them by poifon, which can 
never be generally enough ufed to effed that purpofe. 



/ 


[ 359 ] 


\ 

XX. Experiments and Obfervations on the Diffblution of Metals 
m Acids , and their Precipitations ; with an Account of a new 
compound acid MenJiruum , ufeful in fame technical Operations 
of parting Metals . By James Keir, Efq. F. R . S. 

Read May 20, 1790. 

I N the following Paper, I intend to relate two fets of experi- 
ments ; one 9 fliewing the effects of compounding the vitriolic 
and nitrous acids in dijfolving metals ; and the other, defcribing 
fome curious appearances which occur in the precipitation of 
fiver from itsfolution in nitrous acid by iron 9 and by fome other 
fubfances. In a fubfequent Paper I hope to continue the fubjedt 
of metallic diffolution * and precipitation, firft, by adding fome 
experiments on the quantities and kinds of gas produced by 
diflolving different metals in different acids, under various cir- 
cumftances ; fecondly, by fubmitting certain general propoft ions , 

* The Englifh word folution has two fignifications in chemifiry ; one, expref- 
live of the aft of diffolving, as when we fay, that “ folution is a chemical 
operation and the other, denoting the fubfiance diffolved in its folvent, as 
** a folution of filver in nitrous acid.” The French language is equally equi- 
vocal, as the word “ diffolution” is ufed in both the above-mentioned fenfes. In 
treating on this fubjeft, in which both meanings were very frequently required, 
fometimes in the fame fentence, I could not but be fenfible of confufion in the 
flyle, and X have therefore confined the word folution to exprefs the fubftance 

diffolved together with its folvent, and the word diffolution to denote the ad of 
diffolving. 


which 


r lfyn Mr. Keir’s Experiments and Obfervahons on 

which feem deductible from the fafts related; and, laftly, by 
concluding with fome reflexions relative to the theory oj metallic 

dijfolution and precipitation. 


• part 


I. 


0*2 the effects of compounding the vitriolic and nitrous ac.ds, under 

upon O' dilution of mob. 


SECTION FIRST* 

v 

On the mixture of oil of vitriol and nit) e. 

i. The properties of the feveral acids, in their feparate* 
Rates, have been inveftigated with confiderable mduhry and 
fuccefs; and thofe of one compound, aqua regts, are we 
known on account of its frequent ufe in diffolvtng gold : yet 
not only various other combinations of different acids remain 
to be examined ; but alfo the changes of properties to which 
thefe mixed acids are fubjeft, from the difference of circum- 
ftarices. efpecially thofe of concentration , temperature, and of 
that quality which is called, properly or improperly, phhgiflt- 

cation, are fubjeffs ftill open for enquiry. ■ 

2 . As 1 (hall have frequent cccaiion to fpeak ct the phloqiju 

cation and dephlogiflicvtion c£ acids, I .wife to premife, that by 
thefe terms I mean only certain flates or qualities of _ thofe 
bodies but without any theoretical reference. Thus vitriolic 
acid may be faid to be phlogifticated by addition of fulphur or 
other inflammable matter, by which it is. converted into iol- 
phureous acid, without determining whether this 

6 ' CaU £ 


the Dijfolution of Metals in Acids . 061 

V 

caufed by the addition of the fuppofed principle phlogifion, as 
one let of philofophers believe, or by the aftion of the added 
inflammable fubftance in drawing from the acid a portion of 
its aerial principle, by which the ftflphur, its other dement, is 
made to predominate, as others have lately maintained. It 
were nnich to be wiflied, that w r e had words totally uncon- 
nected with theory ; that chemifts, who differ from each other 
in fome fpeculative points, mav vet fpeak the fame language 
and may relate their fails and obfer nations, without having our 
attention continually drawn afide from thefe to the different 
modes of explanation which have been imagined. But at pre- 
fen t we have only the choice of terms between words derived 
from the ancient theory, and thofe which have been lately 
propofed by the oppofers of that theory. In this dilemma I 
have preferred the ufe of the former, not that I wifli to fhew 
any predilection to either theory, but becaufe that fyftem, hav- 
ing long been generally adopted, is underftood by all parties ; 
and principally becaufe, by ufing the words of the old theory, I 
am at liberty to define them, and to give fignifications expref- 
five merely of fails, and of the aitual Hate of bodies ; whereas 
the language and theory of the antiphlogiftic chemifts being 
interwoven and adapted to each other, the former cannot be 
diverted of its theoretical reference, and therefore feems inap- 
plicable to the mere expofition of fads, but ought to be 
referved folely for the explanation of the doitrines from which 
this language is derived. Thus by the definition which I have 
mentioned of phlogijhcation , this word expreffes not the pre- 
fence or exiftence of an hypothetical principle of inflammabi- 
lity ; but a certain well-known quality of acids and of other 
bodies, communicated to them by the addition of many aftual 
inflammable lubftances. Thus nitrous acid acquires a phlo- 
Vol. LXXX* B b b gifticated 


Mr . Keir’s Experiments and Obfervattons on 
giflicated quality by addition of a little fpirit of wine, or by 

difiillation with any inflammable fubftance. 

3. No two fubftances are more frequently in the hands of 
chemifts and artifts than vitriolic acid and nitre , )et I have 
found, that a mere mixture of thefe, when much concen- 
trated, poffeffes properties which neither the vitriolic acid nor 
the nitrous, of the fame degree of concentration, have imgly, 
and which could not eaflly be deduced, a priori , by lealoning 
from our prefent knowledge of the theory of chemifhy. 

4. Having found by fome previous trials that a mixture 
compofed of nitre diflolved in oil of vitriol was capable of 
diffolving filver eaflly and copioufly, while it did not affect 
copper, iron, lead, regulus of cobalt, gold, and platina, I 
conceived, that it might be ufeful in fome cafes of the parting 
of filver from copper and the other metals above mentioned , 
and having alfo obferved, that the diflolving powers of the mix- 
ture of vitriolic and nitron s acids varied greatly in different 
degrees of concentration and phlogiftication, i thought that an 
mveftigation of thefe effects might be a fubjeft fit fot philo- 
fophical chemiftry, and might tend to illuftrate the theory of 
the diffolution of metals in acids. With thefe views I made 


the following experiments. 

3. I put into a long- necked retort, the contents of which, 
including the neck, were 1400 grain meafures, 100 gram 
meafures of oil of vitriol of the ufual deniity at which it is 
prepared in England, that is, whofe fpecifi c gravity is to that 
of water as 1,844 to 1, and ico grains of pure and clean 
nitre, which was then diiTolved in the acid by the heat of a 
water-bath. To this mixture 100 grains of ftandard filver 
were added ; the retort was let in a water hath, in. which the 


the D/ffclutlon of Metals Hi Acids* 

water w aS made to droll, and a pneumatic apparatus was 
applied to catch any air or gas which might be extricated. 

The filver began to diffolve,and the folution became of a" purple 
or violet colour. No air was thrown into the inverted jar, except* 
mg a little of the common air of the retort, by means of the ex- 
panfion which it fuffered froiti the heat of the water-bath, and 
from fome nitrous fumes which appeared in the retort, and 
which having afterwards condenfed, occasioned the water to' 
nfe along the neck of the retort, and mix with the folution. 
The remamilig filVef Was then feparated and weighed, and it 
was fotlnd that 39 grains had been d i delved ; but probably 
more would have been diffolved if the operation had not been 
interrupted by the Water rufliing into the retort, 

6. In the fame apparatus 2od grains of (kuidard filver werl 
added to a mixture of ido grains of nitre previoufly diifolved' 
m 200 gram-meafures of oil of vitriol ; and in this folveiii’ qi 
giams of the filver were diffolved* Without any produtlion df 
air or Wt The which was of , vi„L colour ‘ ha”, 

ing been poured out of the retort while warm (for with fo‘ 
large a proportion of nitre, fuebi mixtures, efpedally after' 
having diifolved filver, are apt to congeal with fmall degrees of 

cold), in order to feparate the uildiffolved filvef from ' St, and' 

having been returned into the retort without this filver, I 
poured 206 grains of Wafer info' the retort, Upon which a ftron? 
effervefeence took place between the folution and' tfof wafeb’ 
and: 3100 gratn-mealures of nitrous gas were thrown into the" 
invfcrted jar. Upon pouring 200 grains more of water into the 
fetort,' 600 grain-meafufes of this fame gas were' expelled! 
Further additions of water yielded no more gas ; neither did ! 
the filver, wheh afterwards added to this diluted folution, give 

B b b 2 ariy 


64 Mr. Keik’s Experiments and Obfervations on 

any fenfible effervefcence, or fuffer a greater lofs of weight 

than two grains. , . r . 

7 . In the fame apparatus too grains of ftandard filver were 

expofed' to a mixture of 30 grains of nitre diflolved m _oo 
grain -meafures of oil of vitriol; and in this operation, 80 
grains of filver were diflolved, while at the lame time 45 ^ 
Lin-meafures of nitrous gas were thrown into the inverted 
kr. When the undiffolved filver was removed, 200 g.ams of 
water were added to the folution, which was of a violet co- 
lour, and upon the mixture of the two fluids an efferves- 
cence happened ; but only a few bubbles of nitrous gas were 

""I Tthellm. apparatus too grains of ftandard filver wero 
expofed to a mixture of zoo grain- meafu res ot oil of viti.ol, 
200 grains of nitre, and 200 grains of water ; and m ns 
operation 20 grains of the filver were diffolved without any 

fenfible emiffion of air or gas. # , *3 

o In thefe experiments, the copper contained in the ftan 

filvei gave a reddilh colour to the faline mafs which was formed 
in the folution, and feemed to be a calx of copper interfperfed 
through the fait of filver. I perceived no other difference 
between the effects of pure and ftandard filver diflolved in this 

t 

"I I then expofed tin to the fame mixture of oil of vitriol 

and nitre, In the fame apparatus, and in the to arcumftances, 
taking care always to add more metal than could be diffolved, 
that by weighing the remainder, the quantity capable of being 
diffolved might be found, as I had done with the experiments on 

filver : and the refults were as follow. 

, , No tin was diffolved nor calcined by the mixtures in the. 
proportion of aoo grain-meafores of oil of vitriol to aoo gra.no 


the DiJJblution of Metals in Acids. 36^ 

of nitre ; nor by another mixture in the proportion of 200 
grain-meafures of oil of vitriol to 150 grains of nitre, and 
confequently no gas was produced in either inftance. 

12. With a mixture in the proportion of 200 grain-meafures 
of oil of vitriol and 100 grains of nitre, the tin began foon to 
beaded on, and to be diffbfed through the liquor; but no 
extrication of gas appeared until the digeftion had been con- 
tinued two hours in boiling water ; and then it took place, and 
gave a frothy appearance to the mixture, which was of an 
opaque white colour, from the powder of tin diffufed among 
it. In this experiment the quantity of tin thus calcined was. 
73 grains, and the quantity of nitrous gas extricated during 
this adion on the tin was 8500 grain-meafures. Then, upon 
pouring 200 grains of water into the retort, a frefh efferves- 
cence took place between the water and the white opaque mafs, 
and 4600 grain-meafures of nitrous gas were thrown into the 
inverted receiver. 

13. With a mixture in the proportion of 100 grain-meafures 
of oil of vitriol to 30 grains of nitre, 30 grains of tin were 
diffolved or calcined, and the nitrous gas, which began to be 
extricated much fooner than in the laft mentioned experiment 
with a larger proportion of nitre, amounted to 6300 grain- 
meafures. Water, added to this folution of tin, did not pro- 
duce any effervefcence. 

14. With a mixture in the proportion of 200 grain-meafures 
of oil of vitriol, 200 grains of nitre, and 200 grains of water, 

1 33 g r ains of tin were aded on with an effervefcence, which 
took place violently,, and produced 6500 grain-meafures of 
nitrous gas. 

15. The feveral mixtures above mentioned* in different pro- 
portions of nitre and oil of vitriol, did, by the help of the 

heat 


a66 jl/r. K.e i r’s Experiments and Obfervatiom on 

heat of the water-bath, calcine mercury into a white or greyiflt 
powder. Nickel was alfo partly calcined and partly diflblved by 
thefe mixtures. I did not perceive that any other metal was 
affe&ed by them, excepting that the furfaces of fome of them 


were tarnifhed. 

1 6. Thefe mixtures of oil of vitriol and nitre were apt 
to congeal by cold, thofe efpecially which had a large propor- 
tion of nitre. Thus, a mixture of 1000 grain-meafures of oil 
of vitriol and 480 grains of nitre, after having kept fluid 
feveral days, in a phial not fo accurately flopped as to prevent 
altogether the efcape of fome white fumes-, congealed 
at the temperature of 55 ° of Fahrenheit’s thermometer ; 
whereas fome of the fame liquid, having been mixed with equal 
parts of oil of vitriol, did not congeal with a lefs cold than 45 . 
The congelation is promoted by expofure to air, by whiclv 
white fumes rife, and moifture may be abforbed, or by any 

other mode of flight dilution with water. 

17, Dilution of this compound acid, with more or le a 
water, alters confiderably its properties, with regard to its 
aftion on metals. Thus it has been obferved, that in its concen- 
trated ftate it does not aft on «! but, by adding water, it 
acquires a power of afting on that metal, and with different 
effect, according to the proportion of the water added. Thus, 
by adding to two meafures of the compound acid one meafure 
of water, the liquor is rendered capable of calcining iron, an 
forming with it a white powder, but without effervefcence. 
'With an equal meafure of water effervefcence was produced. 

With a larger proportion of water the iron gave alfo a brown 
colour to the liquor, fuch as phlogifticated nitrous acid acquires 
from iron, or communicates to a folution of martial vitriol in 


water. 


18. Dilution 


the Dijfohtwn of Metals in Acids % 

f , I 8 - DiIutIon with water rend ers this compound acid capable 
of diflolvmg copper and zinc, and probably thofe other metals 

w ic are fubjed to the adion of the dilute vitriolic or nitrous 
acids. 


SECTION SECOND. 

An account of a new procefs for feparating fiver from copper. 

19. The properties of this liquor, in diffolving filver eafily 
without a cl mg on copper, have rendered it capable of a very 
ufeful application in the arts. Among the manufadures at 
Birmingham, that of making veffels of filver plated on cop- 
per is a very confiderable one. In cutting out the rolled nlated 
metal into pieces of the required forms and lizes, there ar! 
many Ihreds, or /craps as they are called, unfit for any purpofe 
but the recovery of the metals by feparating them from each 
other. The eafieft and moft oeconotnical method of parting 
thefe two metals, fo as not to lofe either of them, is an object 
of fome confequence to the manufadurers. For this purpofe 
two modes were pradifed ; one, by melting the whole of the 
miired metals with -lead, and feparating them by eiiquation and 
telling ; and the fecond, by diffolving both metals in oil of 
vitriol, with the help of heat, and by feparating the vitriol of 
copper,^ by dillolving i|*in water, from the vitriol of filver, 
which is afterwards to be reduced and purified. In thefirff of 
thefe methods, there is a confiderable w-afte of lead and cop- 
per ; and in the fecond, the quan tity of vitriolic acid employed 
is very great, as much more is diffipated in the form of volatile 

mriohc, or fulphureousacid, than remains in the compofition of 
he two vitriols. 


5 


Some 


„^g Mr . Keiu’s Experiments and Obfervations on 
6 Some years ago, I communicated to an artift the method ot 
cffe( W the reparation of filver and copper by means of the 

above-mentioned compound of vitriolic acid and nitre ; and, as 

1 am informed, that it is now commonly prattled by the ma- 
nufacturers in Birmingham, I have no doubt but it is muc 
more economical, and it is certainly much more eaiily executed 
than any of the other methods : for nothing more is required 
than to put the pieces of plated metal into an eait ien g ax 
pan ; to pour upon them feme of the acid liquor which may 
be in the proportion of eight or ten pounds of oil of vituol 
one pound of nitre; to ftir them about, that the furfaces may- 
be frequently expofed to frefh liquor, and to a i tit a ion y 
a gentle heat from 100* to 200“ of Fahrenheit s leal . 
When the liquor is nearly faturated, the ulver is to e P re ^|' 
tated from it bv common fait, which forms a Iona cornea, eaf ny 
by /citing it in a crucible with a fuffleieut qnantny 
of pof-alh ; and, laftly, by refining the me ted filver, if - 
cellfry, with a little nitre thrown upon it. In tins ma.rae 
filver will be obtained diffidently pure, and the copper w 
remain unchanged. Otherwife, the filver may be pt.c'p.tat. 
in its metallic ftate, by adding to the folution of 
of the pieces of copper, and a fufficient quantity o 

enable the liquor to ad upon the copper. . . . 

The property which this acid mature poffefles of diffolvtng 

filver with great facility, and in confiderable quantity, w, 
probably render it an ufeful menftruum in the leparatton 
filver from other metals, and as the alchemifts have diftin- 
gnilhed the peculiar folvent of gold under the title of J 
Li, a name fufficien.ly diftina.ve, though founded on » 
fanciful allufion t fo, if they had been acquainted with th ^ 


the Djffblutkn cf Metals In Acids* ' 369 

properties of this compound, they would probably have be- 
flowed on it the appellation of aqua regin 


SECTION THIRD* 

The change of properties communicated to the mixture of vitriolic 

and nitrous acids by phlogiflication . 

20. The above-defcribed compound acid may be phlogifti- 
eated in different methods, of which I (hall mention three. 

1 ft, By digefting the compound acid with fulphur by means 
of the heat of a water-bath, the liquor diflolves the fulphur 
with effervefcence, lofes its property of yielding white fumes ; 
and if the quantity of fulphur be fufficient, and if the heat 
applied be long enough continued, it exhibits red nitrous 
vapours, and a flumes a violet colour. 

2dly, If, inftead of diffolving nitre in concentrated vitriolic 
acid, this acid be impregnated with nitrous gas, or with nitrous 
vapour, by making this gas or vapour pafs into the acid, this 
compound will be phlogifticated, as it contains not the entire 
nitrous acid, but only its phlogifticated part, or element, the 
nitrous gas, without the proportion of pure air neceifary to 
conftitute an acid. This impregnation of oil of vitriol with 
nitrous gas or nitrous vapour was firft defcribed, and fome 
of the properties of the impregnated liquor noticed, by Dr. 
Priestley. See Experiments and Gbfervations on Air, Voh 
III. p. 129 and 217. 

^dlv, By fubftituting nitrous ammoniac inftead of nitre in 
the mixture with oil of vitriol. 

21. The compound prepared by any of thefe methods, but 
efpecially by the firft and fecond, differs confiderably in its 

Vol. LXXX. C c c properties 


3 jo Mr. Keir’s Experiments and Obfervations on 

properties with regard to its aftion on metals from the acid de- 
ferred in the firft feftion. It has been obferved, that the 
latter compound has little aftion on any metals but filver, tin, 
mercury, and nickel. On the other hand, the phlogifticated 
compound not only a£s on thefe, but alfo on feveral others. 

It forms with iron a beautiful rofe-coloured folution, without 
application of any artificial heat ; and in time a rofe-coloured 
faline precipitate is depofited, which is foluble in water with 
con fide rable effervefceuce. It diflblves copper, and acquires 
from this metal, and alfo from regulus of cobalt, zinc, and 
lead, pretty deep violet tinges. Bifmuth and regulus of anti- 
mony were alfo attacked by this phlogifticated acid. 

To afcertain more exaffly the effects of this phlogifticated 
acid on fome metals, I made the following experiments, with 
a liquor prepared by making nitrous gas pafs through oil of 

vitriol during a confiderable time. 

22. To 200 grain-meafures of the oil of vitriol impregnated 

with nitrous gas, put into a retort with a long neck, the capa- 
city of which, including the neck, was 1150 grain-meafures, I 
added 144 grains of ftaudard filver, and immerfed the mouth 
of the retort in water, under an inverted jar filled with water, 
to catch the gas which might be extricated. 

The acid began to difiblve the filver with effervefcence by 
application of heat ; the folution became of a violet colour, 
and the quantity of nitrous gas received in the inverted jar was 
J47 oo grain-meafures. Upon weighing the filver remaining, 
the quantity which had been dilfolved was found to be 70 
grains. When water was added to the folution, an effer- 
vefcence appeared, but only a very fmall quantity of gas w^ 
extricated. By means of the water, a white faline powder 0^ 

filver, foluble in a larger quantity of water, was precipitated 

from 


the Dilution of Metals in Acids. 37 1 

from the folutlon. The folution of filver, when faturated and 
undiluted, congeals readily in cool temperatures, and, when 
diluted to a certain degree with water, gives foliated cryftals. 

23. In the fame apparatus, and in the fame manner, 100 
grain-meafures of this impregnated oil of vitriol were applied 
to iron. An effervefcence appeared without application of 
heat, the furface of the iron acquired a beautiful rofe colour or 
rednefs mixed with purple : and this colour gradually pervaded 
the whole liquor, but difappeared on keeping the retort fome 
time in hot water. Notwithftanding a confiderable apparent 
effervefcence, the quantity of air expelled into the inverted jar 
was only 400 grain-meafures, of which \ was nitrous* and 
the reft phlogifticated. The folution was then poured out of 
the retort, and the iron was found to have loft only two grains 
in weight. The folution was returned into the retort, without 
the iron, and 200 grains of water were added to it; upon 
which a white powder was immediately precipitated, which 
re-diflolved with great effervefcence. When 2000 grain-mea- 
fures of nitrous gas had been expelled into the inverted jar 9 
without application of heat, the retort was placed in the water- 
bath, the heat of which rendered the effervefcence fo ftrong, 
that the liquor boiled over the neck of the retort, io that thw 
quantity of gas extricated could not be afcertained. 

24. In the fame manner 1 1 grains of copper were diffolved 
in 100 grain-meafures of impregnated oil of vitiiol. The fo* 
lution was of a deep violet colour, and at laft was turbid. The 
quantity of nitrous gas expelled into the inverted jar during 
the operation was 4700 grain-meafures. When the copper 
was removed, and 200 grains of water were added to the folu- 
tion, an effervefcence took place, 1700 grain-meafuies of 

C c c 2 nitrous 


272 Mr. Keir’s Experiments and Observations on 
nitrous gas were expelled, and the (elution then acquired a 
bl ue colour. 

25. In the fame apparatus and manner, 100 grain-meafures 
of the impregnated oil of vitriol were applied to tin, which 
was thereby diminifhed in weight 16 grains, while the liquor 
acquired a violet colour, became turbid by the fufpenfion of 
the calx of tin, and a quantity of nitrous gas was thrown into 
the inverted receiver equal to 4100 grain-meafures, without 
application of heat, and another quantity equal to 4900 grain- 
meafures, after the retort was put into the water-bath. 

26. Mercury added to the impregnated oil of vitriol formed 
a thick white turbid liquor, which was rendered clear by addi- 
tion of unimpregnated oil of vitriol. In a little time this 
mixture continuing to a£t on the remaining mercury acquired a 
purple colour. The mercury adted upon funk to the bottom of 
the glafs in the form of a white powder, and the purple liquor, 
when mixed with a folution of common fait in water, gave no 
appearance of its containing any mercury in a diffolved ftate. 

27. The nitrous gas with which the oil of vitriol is impreg- 
nated (hews no difpofition to quit the acid by expofure to air; 
but, on adding water to the impregnated acid, the gas is ex- 
pelled fuddehly with great effervefcence, and with red fumes, 
in confequence of its mixture with the atmofpherical air. 

Upon adding 240 grains of water to 60 grain-meafures of 
impregnated oil of vitriol, 2300 grains of nitrous gas were 
thrown into the receiver ; but as the adtion of the two liquors 
is inftantaneous, the quantity of gas expelled from the retort 
before its neck could be immerfed in water, and placed under 
the receiver, muft have been confiderable. The whole of the 

gas, however, was not extricated by means of the water, for 

the 


? 


the Dijfolution oj Metals in Acids., 373 

the remaining liquor diffolved 5 grains of copper, while 8co 
meafures of nitrous gas were thrown into the retort. 

28. The following fails principally are eftablifhed by the 
preceding experiments. 

1. That a mixture of the vitriolic and nitrous acids in a 

» 

concentrated ftate has a peculiar faculty of diffolving filver 
copioufly. 

2. That it ails upon, and principally calcines, tin, mer- 
cury, and nickel; the latter of which, however, it diflblves 
in fmall quantity, and that it has little or no ailion on other 
metals. 

3. That the quantity of gas produced while the metal is 
diffolving is greater, relatively to the quantity of metal dif- 
folved, when the proportion of nitre to the vitriolic acid is 
fmall than when it is large ; and that when the metals are dif- 
folved by mixtures containing much nitre, and with a fmall 
produftion of gas, the folution itfelf, or the metallic fait formed 
in it, yields abundance of gas when mixed with water. 

4. That dilution with water renders the concentrated mix- 
ture lefs capable of diffolving fiver, but more capable of afling 
on other metals. 

5. That this mixture of highly concentrated vitriolic and 
nitrous acids acquires a purple or violet colour when phlogifti- 
cated, either by addition of inflammable fubftances as fulphur,. 
or by its aflion on metals, or by very ftrong impregnation of 
oil of vitriol with nitrous gas 

% Dr. Priestley has noticed this colour communicated to oil of vitriol by- 
impregnation with nitrous gas or vapour, and alfo the effervefcence produced by- 
adding water to this impregnated liquor® See Experiments and Obfervations, 
V0I..III. p. 129 and 2,1 J. 

6 


6, That 


, Mr. Keir’s Experiments and Obfervations on 

. - . 

6 . That this phlogiftication was found to communicate to 
the mixture the power of diffolving, though in fmall quanti- 
ties, copper, iron, zinc, and regulus of cobalt. 

7 . That water expels from a highly phlogifticated mixture of 
concentrated vitriolic and nitrous acids, or of oil of vitriol 
impregnated with nitrous gas, a great part of its contained 
gas ; and that therefore this gas is not capable of being re- 
tained in fuch quantity by dilute as by concentrated acids. 
Water unites with the mixture of oil of vitriol and nitre, 
without any confiderable effervefcence. 

20. To thefe obfervations I fhall fubjoin one other fact, 
namely, that, when to the mixture of oil of vitriol with nitre 
a faturated folution of common fait in water is added, a power- 
ful aqua regis is produced, capable of diffolving gold and pla- 
tina ; and this aqua regis, though compofed of liquors perfectly 
colourlefs and free from all metallic matter, acquires at once a 
bright and deep yellow colour. The addition of urv common 
fait to the concentrated mixtures of vitriolic and nitrous acids 
produces an effervefcence, but not the yellow colour ; for the 
production of which therefore a certain proportion of water 
leems to be neceffary. 


PART II. 

On the precipitation of filver from nitrous acid by iron. 

SECTION i. 

i. Bergman relates, that upon adding iron to a folution of 
filver in the nitrous acid no precipitation enfued * ; although 

* Differt. de Phlog. quantitate in Metallis, 

the 


5 


the TD [[folution t>f Metals in Acids* 

the affinity of iron to acids in general is known to be much 
ftronger than that of filver ; and although, even with regard 
to the nitrous acid, other experiments evince the fuperior 
affinity of iron : for as iron precipitates copper from this acid, 
and as copper precipitates filver, we muft infer the greater 
affinity of iron than of filver. In the courfe of his experi- 
ments, however, fome infiances of precipitation occurred, 
which he attributed to the peculiar quality of the irons which 
he then employed I was defirous of difcovering the circum- 

ftances, 

* Bergman tried many different kinds of iron, and he thought he found two 
which were capable of precipitating filver. But as he did not difcover the cir~ 
cumftances according to which this precipitation fometimes does, and at other times 
does not happen, he may have been miftaken with regard to the peculiar quality 
of thefe two kinds of iron. At leaft the feveral kinds which I have tried always 
precipitated filver in certain circumflances, and always failed to precipitate in 
certain other circumflances. I do not know any other author who has men- 
tioned this fubjeCt, excepting Mr. Kirwan ; who, in the conclufion of his 
valuable Papers on the AttraElive Powers of Mineral Acids , fays, 44 I have always 
64 found filver to beeafily precipitated from its folution in the nitrous acid by iron. 
4 4 The fum of the quiefeent affinities being 62$, and that of the divellent 746'° 
44 Yet Mr. Bergman obferved, that a very faturated folution of filver was very 
44 difficultly precipitated, and only by fome forts of iron, even though the folution 
44 was diluted, and an excefs of acid added to it. The reafon of this curious 
44 phenomenon appears to me deducible from a eircumflance firft obferved by 
44 Scheele, in diffolving mercury, namely, that the nitrous acid when faturated 
44 with it will take up more of it in its metallic form. The fame thing happens 
44 in dilfolving filver in the nitrous acid in a ilrong heat ; for, as I before 
44 remarked, the laft portions of filver thrown in afford no air, and confequently 
44 are not dephlogifticated. Now this compound of calx of iilver, and filver in 
44 its metallic form, may well be unprecipitable by iron, the filver in its metallic 
44 form preventing the calx from coming into contact with the iron, and extracting 
44 phlogifton from it.” In this Paper I fliall not enter into the explanation of 
thefe appearances ; but I thought it neceffary to premife what fo eminent a che- 
mifi: as Mr. Kirwan has fuggeffed on the fubjeCt, that the reader may fee at once 
the prefent ftate of the queftion. I fliall only remark, that the above explana- 


„_g jvfr. Keiu’s Experiments and Obferv aliens on 

fiances, and of inveftigating the caufe, if I fhould be able, of 

this irregularity and exception to the generally received laws of 

affinity. # . 

2. I digefted a piece of fine filver in pure and pale nitrous 

acid, and while the difl'olution was going on, and before the 
faturation was completed, I poured a portion of the lolution 
upon pieces of clean »nd newly-fcraped iron wire into a wine 
glal's, and obferved a fudden and copious precipitation of filver. 
The precipitate was at firft black, then it afiumed the appear- 
ance of filver, and was five or fix times larger in diameter than 
the piece of iron wire which it enveloped. The aftion of the 
acid on the iron continued fome little time, and then it ceafed; 
the filver re-diffolved, the liquor became clear, and the iron 
remained bright and undifturbed in the folution at the bottom 
of the wine giafs, where it continued during feveral weeks, 
without buffering any change, or effe&ing any precipitation of 

the filver. 

2. When the folution of filver was completely faturated, it 
was no longer affefted by iron, according to Bergman’s 

obfervation. . 

4. Having found that the folution aided on the iron, and 

was thereby precipitated, before it had been iaturated, and not 
afterwards, I was defirous of knowing, whether the faturation 
was the circumftance which prevented the aftion and precipita- 
tion. For this purpofe, I added to a portion of the faturated 
folution fome of the fame nitrous acid, of which a part had 
been employed to diflblve the filver-, and into this mixture, 

non, not being founded on any peculiarity in the nature of iron, feems to fup- 
pofe that the filver is alfo incapable of being precipitated, from fuch folut.ons as 
iron cannot aft upon, by any other metal. But this is not the cale = copper and 

, auc readily precipitate filver from thefe folutions. abounding 


the Di folution of Metals In Acids. 377 

abounding with a fuperfluous acid, 1 threw a piece of iron, 
but no precipitation occurred. It was thence evident, that the 
faturation of the acid was not the only circumftance which 
prevented the precipitation. 

5. To another portion of the faturated folution of filver 1 
added fome red fmoking nitrous acid ; and I found, upon trial, 
that iron precipitated the filver from this mixture, and that the 
fame appearances were exhibited as had been obferved with the 
folution previoufly to its faturation. 

6. The fame effects were produced when vitriolic acid was 
added to the faturated folution of filver, and iron afterwards 
applied. 

7. To fome of the fame nitrous acid, of which a part had 
been employed to diffolve the filver, I added a piece of iron ; 
and, while the iron was aifiolving, I poured into the liquor 
fome of the faturated folution of filver; upon which a preci- 
pitation of filver took place inftantly; although, when the 
fame acid had been previoufly mixed with the folution of filver, 
and the iron was then added to the mixture, no precipitation 
had enfued. 

8. The quantity of vitriolic acid, or of the red fuming ni- 
trous acid, neceffary to communicate to the faturated folution 
of filver the property of being adted on by iron, varies accord- 
ing to the concentration, and to the degree of phlogiflication 
of the acids added ; fo that a lefs quantity than is fufficient 
does not produce any apparent efFedf. Neverthelefs, when the 
folution of filver is by addition of thefe acids brought nearly to 
a precipitable ftate, the addition of fpirit of* wine will, in a 
little time, render it capable of adting on iron. 




9. it 


Vol. LXXX. 


Ddd 


3^8 Mr. Keir’s Experiments and Obfervatlons on 

9. It appears then, that a folution of filver is not precipi- 
tated by iron in cold, unlefs it have a fuperabundance of phlo- 
gifticated acid 

10. Heat nffedts the action of a folution of fiver on iron: 
for if iron be digefted with heat, in a perfectly faturated folu- 
tion of filver, fuch as a folution of cryftals of nitre of filver 
in water, the filver will be deposited in its bright metallic 
ftate on different parts of the iron, and the iron which has 
been a£led on by the folution appears in form of a yellow 
ochre. 

1 1 . Bergman relates, that he has fometimes obferved 
beautiful cryftallizations or vegetations of metallic filver formed 
on pieces of iron immerfed long in a folution of filver. 

I have found that no time is able to effect this depofition, un- 
lefs the folution be in a ftate nearly fufficiently phlogifticated 
to admit of a precipitation by iron, but not completely phlo- 
gifticated enough to effiedt that purpofe immediately. 

12. Dilution with a great deal of water ieemed to difpofe 
the folutions of filver to be precipitated by iron more ealily. 

* It was faid, at § 4. that the addition of dephlogifticated nitrous acid to a 
faturated folution of filver did not render this folution precipitable by iron. 
Neverthelefs, as this acid diffolves iron, fuch a quantity may be added, as to 
overcome the counteracting quality of the folution of filver, fo that the acid 
fliall be able to a£t on the iron ; and while this metal is diifolving, it phlogifticates 
the mixture, which then becomes capable of being precipitated, and is in tact 
reduced to the fame Qircumftances as are defcribed at § 7. The limits of the 
quantities which produce changes cannot be aicertained, becauie they depend on 
the degrees of concentration and phlogifiication of the fubitances employed ; 
and therefore, whenever a change is faid to be produced by a certain fubiiance, it 
means that it may be produced by fome proportion, but does not imply by every 
proportion, of that fubiiance. Without attending to thefe confiderations, perfons 
trying to repeat the experiments mentioned in this Paper will be liable to be 
deceived. 


7 


A folution 


the D if elution of Metals in Acids . 

A folution of fiver, which did not a£t on iron, upon being 
very much diluted, and having a piece of iron i miner fed in it, 
during feverai hours, gave a precipitate of fiver in the form of 
a black powder. 

SECTION lit. 

On the alterations which iron or its furface undergoes by the action 
cf a foliation of fiver in nitrous add , or of a pure concentrated 
nitrous acid . 

13. It has been laid, that when iron is expofed to the adtloii 
of a phlogiftica.ted folution of fiver, it inftantly precipitates 
the fil ver, is itfeif acted upon or difiolved by the acid folution 
during a certain time, longer or fhorter, according to the de- 
gree of phlogiftication, quantity of fuperabundant acid, and 
other circumftances, and that at length the folution of the 
iron ceafes 5 the fiver precipitate is re-difioved, if there is fu- 
perfluous acid ; the liquor becomes clear again, but only ren- 
dered a little browner by ijs having diffblved fome iron 3 
while the piece of iron remains bright and undifturbed at the 
bottom of the liquor, where it is no longer able to affedt the 
folution of fiver. 

14* I poured a part of the phlogiflicated folution of filvef 
which had pafled through thefe changes, and which had 
ceafed to act upon the piece of iron, into another glafs, and 
dropped another piece of frefh iron wire into the liquor ; upon 
which I obferved a precipitation of fiver, a folution of part of 
the iron, a rediffolution of the precipitated fiver, and a cefla- 
tion of all thefe phenomena, with the iron remaining bright 
and quiet at the bottom of the liquor, as before. It appeared 

D d d % then* 


o g Q Mr. ICeir’s Experiments and Obfervattons on 

then, that the liquor had not loft its power of atfting owfrejh 
iron, although it ceafed to act on that piece which had been 
expofed to it. 

15. To one of the pieces of iron which had been employed 
in the precipitation of a folution of filver, and from \\hich 
the folution, no longer capable of a fling upon it, had been 
poured off, I added fome phlogifticated folution of ill ver which 
had never been expofed to the aflion ot iron, but no precipi- 
tation happened. It appeared then, that the iron itielf, by 
having been once employed to precipitate a folution 01 lihcr, 
was rendered incapable ot any further aft ion on any folution 
of filver. And it is to be oblerved, that this alteration was 
produced without the lead diminution of its metallic fplen- 
dour, or change of colour. The alteration, howevei, was 
only fuperficial, as may be fuppofed ; for by feraping off its 
altered coat, it was again rendered capable of acting on a folu- 
tion of filver. To avoid circumlocution, I (hall call iron thus 
a ffefted, altered iron ; and iron which is clean, and has not 
been altered, frejh iron. 

x6. To a phlogifticated folution of filver, in which a piede 
of bright altered iron lay, without aflioti, I added a piece of 
frefli iron, which was inftantly enveloped with a mats of pre- 
cipitated filver, and afted on as ufual ; but what is very 
'remarkable, in about a quarter of a minute, or lefs, the 
altered iron fuddenly was covered with another coat of 
precipitated filver, and was now afled on by the acid folution 
like the frefh piece. I11 a little time the filver precipitate was 
re-diffolved, as ufual, and the two pieces of iron were reduced 
to an altered ftate. When a frefh piece of iron was then held 
in the liquor, fo as not to touch the two pieces of altered iron* 
they were neverthelefs foon afted upon by the acid folution, 

6 ' “ d 


I 


the Difolution of Metals in Acids. jS c 

and fuddenly covered with filver precipitate as before; and 
thefe phenomena may be repeated with the fame foliation of 
filver, until the fuperfluous acid of the folution becomes fa~ 
turated by the iron, and then the re-diffolution of the precipi- 
tated filver mu ft ceafe. 

17. I poured feme dephlogifticated nitrous acid on a piece 
of altered iron, without any adlion enfuing, although this acid 
readily afted on frefh iron, and when to the dephlogifticated 
nitrous acid, with a piece of altered iron lying immerfed in it, 
1 added a piece of frefh iron, this immediately began to dif- 
folve, and foon afterwards the altered iron was aded on alfa 
by the acid. 

18. I poured upon a piece of altered iron a folution of cop- 
per in nitrous acid ; but the copper was not precipitated by the 
iron ; neither did this iron precipitate copper from a folution of 
blue vitriol. 

19. Altered iron was aded on by a dilute phlogifticated ni- 
trous acid ; but not by a red concentrated acid, wiiich is 
known to be highly phlogifticated. 

20. I put fome pieces of clean frefh iron wire into a con- 
centrated and red fuming nitrous acid. No apparent adion 
enfued; but the iron was found to be altered in the fame man- 
ner as it is by a folution of filver ; that is, it was rendered 
incapable of being attacked either by a phlogifticated folution 
of filver, or by dephlogifticated nitrous acid. 

21. Iron was alfo altered by being immerfed fome little 
time in a faturated folution of filver, which did not fhew any 
vifible adion on it. 

22. The alteration thus produced on the iron is very fuper- 
ficial. The leaft rubbing expofes fome of the frefh iron be- 
neath 


j82 Mr. Keir’s "Experiments and Obfcrvations on 

neath the furface, and thus fubjects it to the adion of the 

acid. 

It is therefore with difficulty that thefe pieces of altered 
iron can be dried, without lofmg their peculiar property. For 
this reafon, I generally transferred them out of the folution ot 
liiver or concentrated nitrous acid into any other liquor, the 
effects of which I wanted to examine. Or they may be 
transferred firft into a glafs of water, and thence into the 
liquor to be examined. But it is to be obferved, that ii they 
are allowed to remain long in the water, they lofe their pecu- 
liar property or alteration. They may be preferved in then- 
altered ftate by being kept in fpirit of lal ammoniac. 

23. To a faturated folution of copper in nitrous acid (which 
was capable of being readily precipitated by fieffi lton^ J added 
lome faturated folution of filver. From this mixture a piece 
of frefh iron neither precipitated filver nor copper : nor did the 
addition of fome dephlogifticated nitrous acid effed this pre- 
cipitation. 

24. A folution of copper, formed by precipitating filver 
from nitrous acid by means of copper, was very reluftantly and 
{lowly precipitated by a piece or frefh iron , and the iron thus 
afted on by the acid was changed to an ochre. 

25. A faturated folution of filver having been partly preci- 
pitated by copper, acquired the property of acting upon rrefn 
iron, and of being thereby precipitated. 

26. Frefh iron immerfed fome time in folutions of nitre of 
lead, or of nitre of mercury in water, did not occafion any 
precipitation of the diffolved metals ; but acquired an altered 
quality, Thefe metals then in this refpedt referable filver. 

27. It is well known, that a folution of martial vitriol, 

added to a folution of gold in aqua regis 3 precipitates the gold 

in 


the Dijfoluiion of Metals in Acids. 2 g„ 

in its metallic ftate. I do not recoiled!, that the precipitation 
of a iolution of filver by the fame martial vitriol has been ob- 
leivcd. however, upon pouring a Iolution of martial vitriol 
into a folution of filyer in the nitrous acid, a precipitate will 
be thrown down, which acquires in a few minutes more and 
more of a metallic appearance, and is indeed perfed fiver. 
When the two folutzons are pretty concentrated, a bnpht ar- 
gentine film fwims on the furface of the mixture, or filvers 
the tides of the glafs in which the experiment is made. When 
a phlogifticated iolution of filver is ufed, the mixture is black- 
ened, as happens generally to a folution of martial vitriol, 
when a phlogifticated nitrous acid is added to it. 

I added about equal parts of water to a mixture of a phlo- 
gifticated folution of filver and a folution of martial vitriol, in 
which all the filver, had been precipitated, and digefted the 
diluted mixture with heat, by which means mail of the pre- 
cipitated filver was re-diffolved. Bergman has obferved a 
fimilar re-diffolution of gold precipitated by martial vitriol upon 
boiling the mixture ; but he attributes the re-difiblution to the 
concentration of the aqua regis by the evaporation. As this 
explanation did not accord with my notions, I diluted the mix- 
ture with water, and found that the fame re-diffolution occur- 
red both with the folution of filver and with that of gold. 
But vvith neither of the metals did I find that the re-diflolution 
evei took place, unlefs there had been a fuperabundant acid 
in the folutions of gold and filver employed. 

28. Mercury is alfo precipitated in its metallic ftate from its 
folution in nitrous acid by a folution of martial vitriol. When 
the liquor is poured off from the precipitate, this may be 
changed into running mercury by being dried near the fire. 

29. I 


S 8 + 


Mr. Keir’s Experiments, &c. 

,q I found alfo, that fiiver may be precipitated m its me- 
OlBc'tott. from its folu.ioi, in vitriolic sad. by addition or 
a rotation of martial vitriol. A vitriol of mercury may alfo 
be decompounded by a foliation of martial vitriol, and the mer- 
cmial precipitate, which is a black powder, forms globules, 

.when dried and warmed. • , • • , 

30 Luna cornea is not decompounded by martial vitriol ; 

■ confidently there is no operation of a double affinity. Never- 

thelefs, this luna cornea may be decompounded by the elemen s 

of martial vitriol, while they are in the aft of dilution , 

that is, the ffiver may be precipitated in its metallic a e, . y 

digefting luna cornea with a dilute vitriolic acid to which 

feme pieces of iron are added. And it is to be obferved, that 

this redudion of the ftlver and precipitation take place, while 

the acid is yet unfaturated. Marine acid and iron applied to 

luna cornea effed the fame redudion of the filver to a meta ic 

date, even when there is more acid than is fufficient for both 

The explanation of thefe phenomena will he attempted 
the fubfequent Papers which I propofe to prefent on this fub- 

jed to the Society. 



! 


/ 


[ 3 « S ] 


XXL Determination of the Longitudes and Latitudes of fine 
remarkable Places near the Severn . In a Letter from Edward 
PigoU'j Efq> to Sir Henry C. Englefield, Bart . K R* S . 


Read May 20, 1790. 

A S perhaps this Paper may be thought of fome ufe, I beg 
you will do me the favour of preferring it to the Royal 
Society. Its principal objedl is to fettle the longitude and lati- 
tude of feveral remarkable places near the Severn, the relative 
diftances of which I meafured trigonometrically during my 
flay in Giamorganfliire. As they are all deduced from Frarap- 
ton-houfe, it is requifite to determine the pofition of' that place 
with corredtnefs. My father has already given its longitude in 
the Philofophical Tranfactions, Vol. LXXL being the mean 
of feveral obfervations of Jupiter’s firft and fecond fatelliteSo 
From the known ability of the obferver, we may undoubtedly 
depend that all poffible exa&nefs was obtained, of which thofe 
obfervations are fufceptible ; but at that time the fuperior accu- 
racy of the lunar tranfits was not known ; therefore at prefent 
there can be no hesitation in giving the preference to the fol- 
lowing refults. 


Vol. LXXX. 


E e e 


Difference 


2 8 6 Mr. Pigott^s Determination of the Longitudes and 


Difference 

of longitudes in 

time between Greenwich and 

Frampton-houfe, deduced 
of the moon’s limbs. 

from obferved meridian trail fits 

Dates. 

Difference of 

Stars obferved with J . 


meridians, weft. 

G. Greenwich. F. Frampton. 

i 7j 8 
Oct. 3. 

/ // 
14 28- 

(3 Aqnilce at G. and F.. 

15. 

14 36 

y Aquilae at G. and F. 



^ D obferved only at 3 wires at F. 

Nov. 25. 

14 25 + 

i v zz and Mayer’s N° S91. at F. 
bFomalhant at G. 

Dec. 26. 

14 28 

r l ZZ v X at F. 
i« V a b at G. 

1779 



Deb. 22o 

14 26 — 

r > 8 ? 8 at F. 
Ut« Ceti at G. 

27. 

14 3 1 

y 22 at G. and F. 

Mar. 24. 

H 37 

ry Canis maj. J n atF. 
1 <* b « Sb at G. 

30. 

14 41 

r b n# at F. 

1 « b a Sb at G. 

3 To 

14 37 

r e “»1K, at F. 
{« b at G. 

3 l - 

i 4 43 ” 

Ditto, ditto. 



r D obferved only at two wires at F ; but 

Apr. 24= 

14 27 + 

4 they agree. 

1/3 m at G. and at F. 

May 2 2 « 

14 26| 

a Sb at G. and at F. 

Oft. 22. 

H 33 i 

Fomalhaut at G, and at F. 

Biff, of meridians 14 32+ on a mean. * 


Thefe are all the obfervations I have reduced except three 
doubtful ones, which were computed merely out of curiofity. 


Latitudes . of fame remarkable Places near the Severn. 387 


VI 

CO 

j n 

r D and Ardurus ; 10 + hours interval 

Nov. 1. 

14 20 — 

4 going of clock uncertain $ F. 


a . V at G. 

5 obfkrved only at two wires. 


S°* 

14 47 

4 D and Ar&urus ; 12J hours 

interval $ 



b going of dock uncertain. 


3 7 79 




Apr. 26. 

14 > 4 .i 

J D obferved only at three wires, 
l do not agree ; F. 

and they 


This method of determining terreftrial longitudes I have 
fully detailed in the Philofophical Tranfadlions, VoL LXXVI. 
and ftill think it cannot be too ftrongly recommended. The 
preceding additional fet of refults do further corroborate the 
reliance that may be put on it, though the obfervatlons were 
not made with that intention, and confequently feveral of 
th em are deficient in many particulars : their agreement, never- 
thelefs, is conclufive, and infinitely more fatisfadlory than 
could be expedted. Since the above-mentioned publication I 
have been informed, that M. le Marquis be Chabert and 
others, many years ago, fettled differences of meridians on 
fimilar principles, and I dare fay with as much fagacity as the 
then imperfedt ftate of the method would permit. At prefent 
it is certainly confiderably improved, being fufceptible of very 
great exadtnefs and facility, which perhaps may be confidered 
as the foie requifites for rendering it any wife ufeful. 

The latitude of the fame place, taken with an 18-inch 
quadrant made by Bird, is thus by my obfervations 1 


E e e 2, 


5i 


3; gg Mr. Pigott’s Determination of the Longitudes and 


51° 25 o by (3 Geminorum. 

51 24. 50 by e Bootis; two obfervations* 

51 2 5 5 by 7T Sagittarii. 

51 25 13 by 7 Virginis. 

51 24 55 by y Bootis ; two obfervations. 

51 24 48 by y Delphini. 

51 24 56 by Fomalhaut. 

51 24 58 -fon a mean. 

r ditto, by my father, with the fame inftrument« 
5125 1 1 See Phil. Tranf. Vol. LXXI. 

w 1 11 ■' 1 1 — 

51 25 o -latitude of Frampton-houfe on a mean. 


Having thus fettled the pofition of the Obfervatory, I may 
now proceed to give the particulars of the trigonometrical 
operations. 

1 meafured the fame bafe three times by different methods, 

20464 

the refuifs were 2042 l feet. As the view from its extremities 

2042J 

was very confined, another bafe of 1861 yards was deduced 
from it, fituated on the high lands that edge the Severn, hav- 
ing a very extenfive and beautiful profpeft. F rorn the extre- 
mities of this fecond bale, all the angles were taken with a 
tolerably good theodolite on which two minutes might be 
eafily read off. The refults here given are the diftances from 
the various places to the weftern extremity of their bafe, their 
perpendicular diftances to its meridian, and its diftance from . 
thefe perpendiculars*: 

1 1 . . ■' . ; . ^ ■ 

Diftances^ 



Latitudes of fome remarkable Places near the Severn. 


Diftances in yards, 

. - ' 

X TV. Q- 

To the 

To the per- 


Uireuc. 

meridian. 

pendicular. 

• 

33°7 

1254 E 

3059 N 

Frampton-houfe, 

4 S 6 S 4 

42239 E 

1 73 2 4 s 

Brin Hill, the center. 

36928 

21853 E 

29768 s 

Qnantock Hill, the eaft part 0 . 

4O446 

1 S5S6 E 

37322 s 

Land Mark, a tower. 

35543 

11542 E 

33617 s 

Watchet Hill, the center. 

2191 1 

1465 E 

21862 s 

Minehead. 

21336 

6664 w 

20268 s 

Porlock, or Blufton Foint 0 . 

30238 

23152 w 

19450 s 

Leemouth. . . 

46264 

40398 w 

22547 s 

Hangman Hill. 

292 1 

2842 w 

673 N 

St. Donat’s Caftle, 

1564 

491 E 

1483 N 

Llantwit Church, 

10140 

448 w 

10 i 30 N 

Llangwynewar Hill, eaiFp &ZU... 

25126 

2299 E 

25020 N 

A remarkable hill. 

3 ] 35 

2063 E 

2361 N 

Llanmace Church. 

8864 

5906 E 

6609 N 

St. Elilary’s Church. 


The direct diftances are the moft accurate, the others being 
affeded according to the exadnefs of the meridian of the weft 
extremity of the bafe ; the diredion of which was found by 
the variation needle, its declination having been determined at 
Frampton-houfe, and therefore fufficiently corred ; for an 
error in that angle, even of half a degree, would make a dif- 
ference of a very few feconds in any of the places obferved. 

The following are the longitudes and latitudes of the fame 
places, deduced by Gen. Roy’s moft accurate and ufefuL 
tables, (hewing the value of each degree, &c*. 


Longitudes 


Mr . Pigott’s Determination , &c. 



Longitudes well of 
Greenwich, 

Latitudes 

North. 


in time. 

in deg. &c. 


/ // 

0 / // 

0 / // 

j 

' 

12 24- 

3 5 58 

5 1 *4 5 6 i 

Brin Hill, the center. 

13 28- 

3 21 57 

51 8 48 § 

Quantock Hill, eaft part. 

1 3 47 i 

3 26 52 

5 1 5 5 

Land mark, a tower. 

14 0 + 

3 3 ° i\ 

5 1 6 55 

Watchet Hill, the center. 

H 

3 34 23 

51 26 44 § 

St. Hilary’s Church. 

\ 14 29— 

3 37 12 

5 1 35 49 

A remarkable Hill. 

14 291 

3 37 24 

5 1 24 39 

Llanmace Church. 

! H 3 1 ! 

3 37 52 

5 1 12 42I 

Minehead. 

14 32+ 

3 3 8 2 

5i 25 0- 

Frampton-houfev 

j 14 341 

3 38 38 

51 24 13 

Llantwit Church. 

14 36+ 

3 39 1 

5 1 23 29 

Station, weft extremity of the bafe. 

14 37 s 

3 39 22 

51 28 281 

Llangwynewar Hill, eait part. 

j 14 45 

3 41 15 

5 1 23 49 

St. Donat’s Cattle. 

M 57 - 

3 44 14 

51 J 3 29! 

Porlock or Hufton Point, 

15 4 «i 

3 57 7 

5 i *3 54 

Leemouth. 

1 l6 42| 

4 10 35 

51 12 22 

Hangman Hill. 


The names of the places here fet down were pointed out to 
me by perfons who feemed well acquainted with the fur- 
rounding country. The breadth of the Severn at that part 
where I took the angles is about 12I. miles. However coarfe 
thefe trigonometrical operations may appear, when compared 
to thofe made fo fcientifically, and with fuch wonderful 
exaftnefs, in the fouthern parts of the kingdom, they never- 
thelefs fettle the geographical fituations of the given places 
with more precifion than is ufually obtained, even from a feries 
of aftronomical observations. 

Perhaps fome gentlemen in the north of Devonfhire or So- 
me r let friire may be induced to continue fimilar operations, when 
they coniider with what little trouble they may be made, as 
the diftances between any of the towns I have determined may 

jfuffice for a bafe 0 


1 




39 1 


XXII. Experiments and Obfervations on the Matter of Cancer 9 
and on the aerial Fluids extricated from animal Subfances by 
Dif illation and Putrefaction ; together with fame Remarks on 
fulphureous hepatic Air . By Adair Crawford, M, D. F. R. & 


Read June 17, 17900. 

^T^HRRE are feveral varieties In the colour and Confidence 
A of the matter difcharged by cancerous ulcers. It is in 
fome cafes of a pale afh colour; in others, it has a reddifh 
caft ; and in many indances it has more or lefs of a brown 
tinge, fometimes approaching nearly to black. Its confidence 
is for the mod part thin ; but in the cancerous, as well as in 
other malignant ulcers, we frequently meet with a white fordes P 
vvhiCii cloiely adheres to the furface of the fore, and which 
appears to be fcareely mifcible with water. In the fame pa- 
tient the appearance of the difcharge is frequently varied by 
internal remedies, or by external applications; but If we ex- 
cept the temporary variations produced by accidental circum- 
ftances, the cancerous ulcer is, in its advanced dage, very ge- 
nerally accompanied with a peculiar odour more highly fetid 

and offenfive than that which is emitted by other malignant 
ulcers. 

It is well known, that the cancerous matter occafions by its 
abforption fchirrous tumors of the lymphatic glands conti- 
guous to the parts alfedted ; and that it gradually corrodes the 

branches 


2 2>. Crawford’s Experiments on the Matter 

branches of the larger blood-veffels, which have a peculiar 
power of refitting the adion of other purulent dilcharges. 

' A pprehending that fome light might poffibly be thrown upon 
the nature of cancerous, difeafes, by enquiring into the proper- 
ties of this fubftance, I procured a portion ot it from a patient 
who had for feveral years been afflicted with a cancer ni the 
breaft. Having diffufed it through pure water, I divide 1 
into three parts, which were put into lma g as ve w s . . 
one of thefe I added a folution ot vegetable fixed aUali, 
the fecond, a little concentrated vitriolic acid ; and to the 
third, fyrup of violets. By the vegetable hxed alkali no en- 
able change was, produced : upon the addition of the vitriolic 
acid, the liquor in the fecond glais acquired a deep brown co- 
lour a brilk effervefcence took place, and at the lame time 
the peculiar odour of the cancerous matter was greatyen- 
: c reafed, and diffufed itfelf to a confiderable diftance through 
the furrounding air. The fyrup of violas communicated to 

the liquor in the third glafs a faint green colour 

The cancerous matter ufed in thefe experiments had a 
-brovrnifh -caft. It had been imbibed by cotton, an ept or 

ifome days before the trials were made. ^ 

Mr. Geber has fhewn, that animal fubftances upon aei 

firft putrefadion do not effervefce with acids ; that, after t e 

proceft & continued for fome time, a mnnifeft 

takes piece ; and that this efifcS agam d.fappeats betote me 

.putrefa&ion has ceafed. . 

Sufoeding that the effervefcence in the preceding experim 
might have, arifen from a change which the matter un erwent 
in "confequence of its having been kept fome days before the 
trial was made, I repeated the experiment with a port, . 
•ireddiih matter recently obtained from a cancerous penis. P 




of Cancer, and on Animal Hepatic Air* 393 

the addition of the acid, the liquor, as before, acquired a brown 
colour, its fetor was much increafed, and a manifeft effervef- 
cence took place, although it was not fo confiderable as in the 
former inftance. A portion of the fame matter diffufed through 
diftilled water communicated a blue tinge to tindture of litmus, 
and a greenifti caft to fyrup of violets. 

It is proper to obferve, that when fyrup of violets was mixed 
with portions of cancerous matter from a variety of different 
fubjedts, the change produced was in fome cafes fcarcely per- 
ceptible ; but in every inftance the prefence of an alkali was 
detedled by dipping into the matter a flip of paper that had 
been previoufly tinged blue by tindlure of litmus, and after* 
wards flightly reddened by acetous acid. The red colour was 
invariably in the courfe of a few minutes abolifhed, and the 
blue reftored. 

The cancerous matter, as has been already remarked, ac* 
quired, upon the addition of the vitriolic acid, a brown hue. 
It is well known, that this acid, when it is highly concen* 
trated, communicates a brown or black colour to all animal and 
vegetable fubftances. Being deiirous of learning whether th& 
change which took place upon the addition of the acid to the 
cancerous matter in this experiment, was different from that 
which would be produced by the fame acid in other animal 
fubftances, and particularly in recent healthy pus ; I took 
equal quantities of the latter, and of afh- coloured cancerous 
matter, and having diffufed each of them through thrice its 
weight of diftilled water, I added to them equal quantities of 
concentrated vitriolic acid; the weight of the acid being nearly 
the fame with that of the matter ufed in the experiment. The 
mixture containing the pus acquired from the acid a faint brown 
colour; but that which contained the cancerous matter, was 
Vol. LXXX. F f f fuddenly 


394 Dr. Crawford's Experiments on the Matter 

fuddenly changed to a deep brown, approaching to black. 
When thefe mixtures were diluted with about twice theic 


weight of diftilled water, the brown tinge of the former en- 
tirely difappeared; but the latter ftill retained its brown colour, 
although it was fomewhat fainter than it had been upon the firfb 
addition of the acid. 

The aerial fluid which was difengaged in the foregoing trials 
from the matter of cancer, by the vitriolic acid, appeared from 
its odour to have a nearer refemblance to hepatic than to any 
other fpecies of air. As it feemed, trom its lenfible qualities, 
to be a very aftive, and probably a deleterious principle, I 
endeavoured more particularly to enquire into its nature, and 
to compare it with common hepatic air. But before I i elate 
the trials which were made with that view, it may not be im- 
proper briefly to mention the characters by which common he- 


patic air is diftinguiftied. 

It has a fmell refembling that of rotten eggs ; it is inflam- 
mable, and during its combuftion in the open air, fulphur is 
depofited; it communicates a black colour to filver and copper, 
and a brownifh tinge to lead and iron ; it is foluble in water, 
and when a folution of nitrated filver is dropped into water 


impregnated with it, the mixture becomes turbid, and a dark- 
coloured precipitate falls to the bottom ; by the addition of 
the nitrated filver, the odour of the hepatic air is rendered 
much fainter; and it is entirely deftroyed by concentrated nir 
trous, or by dephlogifticated marine acid. 

To determine whether the aerial fluid contained in the can- 
cerous matter poflefled thefe properties, a portion of this fub- 
ftance was diffufed through diftilled water. The mixture 
being filtered, a'fmall quantity of nitrated filver was dropped 
into it. In a little time, an afh-coloured cloud was produced. 


of Cancer , and on Animal Hepatic Air . 595 

which foon afterwards acquired a brownifh purple hue, and at the 
end of two hours the colour of the mixture was changed to a deep 
brown. The fetid fmell was now rendered much fainter than 
that of a fimilar mixture of cancerous matter, and of diftilled 
water, to which nitrated filver had not been added. When a 
little concentrated nitrous acid was dropped into the mixture 
which had been thus altered by the addition of nitrated filver, 
a flight effervefcence took place, the brown hue was inftantiy 
changed to an orange colour, and the fetid fmell was abolifhed* 
The fetor was likewife entirely deftroyed, when dephlogifti- 
cated marine acid was added either to cancerous matter in its 
feparate ftate, or to a portion of that fubftance which had been 
previoufly mixed with nitrated filver. 

By the foregoing properties the cancerous virus is diftinguifhed 
from common pus : for when dilute vitriolic acid is added to com* 
mon pus, no effervefcence is produced ; and when a foluticn of 
nitrated filver is dropped into this fubftance previoufly diffufed 
through diftilled water, the mixture does not acquire a brown co- 
lour ; nor does any fenfible precipitation take place for feveral 
hours. It appeared, however, that when the laft experiment was 
repeated with matter obtained from a venereal bubo, the mixture 
upon the addition of the nitrated filver became flightly turbid, 
and, at the end of two hours, it acquired a brownifh caft. The 
fame effects were perceived when the trial was made with mat- 
ter obtained from a carious bone. But in thefe in fiances the 
precipitation was much lefs confiderable than that which was 
produced by the cancerous matter. 

I next endeavoured to procure, in its feparate ftate, a por- 
tion of the air which is extricated from the matter of cancer 
by the vitriolic acid. With this intention a quantity of red- 
difh cancerous matter was mixed in a fmall proof, with about 

F f f 2 ? thrice 


j)r, Crawford’s Experiments on the Matter 

thrice its weight of diftilled water. To this mixture a littie 
vitriolic acid was added; upon which an eftervefcence took 
place, and the air that was difengaged was received iu a 
phial over mercury. When one half of the mercury was 
expelled from the phial, the latter was inverted over diftilled 
water, and the portion of the mercury that remained in it 
being fuffered to defeend, and the water to rife into its place, 
the phial was clofely corked. The air and water were then 
brilkly agitated together, and the phial being a fecond time 
inverted over diftilled water, the cork was removed ; when 
it appeared by the heighth to which the water rofe, that a 
part of the air had been abforbed. The water contained in 
the phial was now found to be ftrongly impregnated with the 
odour of the cancerous matter, and a little nitrated diver being 
dropped into it, a purplifh cloud, inclining to red, was pro- 
duced. It is proper to obferve, that the change of colour upon 
the addition of the nitrated filver, in this experiment, was at 
iirft fcarcely perceptible ; but in the courfe of a few minutes 
it became very diftindh As it might perhaps be doubtful, 
whether this alteration would not be produced in the nitrated 
filver by expofure to the air alone, the colour of the mixture 
was compared with that of a fimilar mixture of nitrated filver 
and of pure diftilled water, which had remained expofed to 
the open air for an equal length of time. Although a flight 
change of colour was produced in the latter inftance, yet it 
was much lefs confiderable than that which took place in tne 
former. 

In the above recited experiment, the air came over mixed with 
the common air that was contained in the proof, i he quantity 
of aerial fluid that can be thus extricated by the addition of 

the acid without the affiftance of heat, is not very confiderable. 

If 


of Cancer , and on Animal Hepatic Air . 397 

If heat be applied, a larger portion of fetid air, having the 
odour of cancerous matter, may be difengaged ; but in that 
cafe it will be found to be mixed with vitriolic acid air. 

With a view to obtain the former of thefe fluids in as pure 
a ftate as poffible, the experiment was repeated in the follow- 
ing manner, A portion of the cancerous virus, diffufed 
through diftiiled water, was introduced into a fmal! proof ; a 
little vitriolic acid was added ; the veffei was filled with dis- 
tilled- water, and a crooked tube, alfo filled with that fluid, 
was fixed to its neck. The extremity of the tube being then 
introduced into the mouth of an inverted bottle containing 
water, and the flame of a candle being applied to the bottom 
of the proof, a quantity of air was expelled, which was re- 
ceived in the bottle. This air, when it was fir ft difengaged, 
rofe in the form of white bubbles ; it had a very fetid frnell, 
fimilar to that of the cancerous matter ; and the water which 
was impregnated with it occafioned a dark-brown precipitate 
in a foiution of nitrated filver. The crooked tube being fepa- 
rated from the proof, a very offenfive white vapour, refembling 
in its odour the air extricated during the experiment, arofe 
from the mixture, and continued to afcend for nearly half an 
hour. When to a portion of this fmoking liquor, previoufly 
filtered, a little concentrated nitrous acid was added, the fetid 
fmell was entirely deftroyed, a flight effervefcence took place, 
and a flaky fubftance that floated through the mixture was 
difengaged. 

The foregoing experiments prove, in general, that the fetid 
odour of the matter of cancer is increafed by the vitriolic, but 
entirely deftroyed by the concentrated nitrous and dephlogifti- 
cated marine acids ; that the aerial fluid, which is difengaged 
by the vitriolic acid, is foluble in water; and that the foiu- 
tion 


1 


298 Dr. Crawford’s Experiments on the Matter 
tion depofits a reddifti brown precipitate upon the addition of 
nitrated filver. Whence it follows, that the cancerous matter 
contains a principle which has many of the properties of he- 
patic air, and which may perhaps not improperly be termed 

animal hepatic air. 

It has moreover been (hewn, that the matter of cancer is 
impregnated with an alkali which is in fuch a (fate as to change 
the colour of vegetable tinftures. I had very little doubt that 
this was the volatile alkali : for it is well known, that putrid 
animal fubftances frequently abound with that fait ; but have 
never, I believe, been found to contain a fixed alkali in a dif- 
engaged date. With a view, however, more decifively to 
determine this point, I tried the following experiment. A 
quantity of cancerous matter, diffufed through diftilled water, 
was introduced into a glafs retort to which a receiver was 
adapted. The mixture was (lowly diftilled by means of a fand 
heat ; and a fmall quantity of the liquor which came over into 
the receiver being poured into an infufion of Brazil wood, in- 

ftantly imparted to it a deep red colour. 

Hence it clearly appears, that the alkali contained in the 

cancerous matter was the volatile, becaufe it was feparated by 

diftillation with a heat which did not exceed that of boiling 
water. 

It feemed extremely probable, that the above-mentioned 

alkali was united to the aerial fluid with which the matter of 

cancer is impregnated. Of the truth of this fa£t I was per- 

fuaded by dbferving, that the fmell of the cancerous matter 

was greatly iucreafed by the addition of the vitriolic acid : for 

I could fcarcely avoid concluding, that this phenomenon arofe 

from an union between the acid and alkali, in confequence of 

which the odoriferous principle was extricated by a fuperior 

attra&ion. 


of Cancer , and on Animal Hepatic Air. 29 9 

attraction* This conclufion will be confirmed by experiments 
to be recited in the fequel, which prove, that the volatile alkali 
is capable of entering into a chemical combination with the 
aerial fluid contained in the matter of cancer* 

Of the eitr extricated front cancerous matter , and from other 

animal fubjlances, by d filiation. 

A portionof matter from a cancerous bread was di.fFu.fed through 
diddled water, and introduced into a fmall coated glafs retort, 
which was gradually expofed to heat in a fand bath till the bottom 
oi the retort became red-hot. The neck of the latter was intro- 
duced below an inverted jar filled with water, and a quantity 
of air was received in the jar, which was found to confid of the 
common air contained in the retort. Two meafures of it, 
mixed with one of nitrous air, occupied the fpace of a little 
lefs than two meafures. This portion of air was ftrongly im- 
pregnated with the peculiar fmell of the cancerous matter. 

The heat continuing to increafe, the water began to boil, 
and a large quantity of aqueous vapour a rofe which, as foon 
as it came into contaft with the common air, produced a white 
fmoke. The fmell that was now perceived was remarked by 
thole who Were prefent to be fimilap to that of frefh animal 
fubdances when they are boiled. The aqueous vapour in this 
part of the procels was not mixed with any permanently eladic 
fluid. / 

When the greater part of the water was evaporated, the jar 
containing the fird portion of air was removed, and the neck 
of the retort was introduced beneath an inverted vefl'el filled 
with mercury. Soon after this, a conflderable quantity of air, 
having a fetid imell fimilar to that of burned bones, was extri- 
1 catech 


QO Dr . Crawford’s Experiments on the Matter 

cate d This aerial fluid was mixed with a yellow empyreu- 
matic oil. A portion of it being agitated with water was 
found to be pertly imbibed by that fluid , and nitrated fnver, 
dropped into the water thus impregnated, produced a reddilh 

precipitate, _ 

One meafure of the air, obtained in the foregoing expert- 

ment, being mixed over mercury with an equal bulk or alka- 
line air, the volume of the mixture was found gradually to 
decreafe ; and, at the end of three hours, the a.r in the tube 
occupied the fpace of only one meafure and two tenths. An 
oily depofit was now made upon the inner furface of the u e. 
At the expiration of eight days, the interior furface of the 
tube was covered with flender films, which had a yellowilh 
4paft, and which were irregularly fpread upon it. e upper 
furface of the mercury within the tube was corroded ; in iome 
places it had a reddilh burnilhed appearance ; m others, it was 
changed into an alh-coloured powder, interlperfed with brown 
foots. The tube was now removed from the mercury and 
the air that remained in it had a llrong fetid fmell, refembhng 

that of burned bones. 

' It has been already obferved, that before the water was «>■ 
tirely 'evaporated, the vapour had loft the odour of the can- 
cerous matter, and had acquired that of animal fubftances 
recently boiled. Hence it appears, that the matter upon which 
the peculiar fmell of cancerous ulcers depends, is a very vo a 
' tile fubftance, for it efcaped at the beginning of the pro«&| 
It alfo appears, that this volatile fubftance, which is probably 
the aftive principle in the matter of cancer, is not changed, y 
limule expofure to heat, into a permanently elaftic fluid , 
the air that efcaped at the beginning of the procefs, although 
it fuelled ftrongly of the cancerous matter, was foun J 


I 


of Cancer , and on Animal Hepatic Air . 40 1 

Priestley’s teft to be as pure as common air; and it was 
evident, that the aqueous vapour which came over in the mid- 
dle of the procefs was not mixed with any permanently 
elaftic fluid ; becaufe, when this vapour was received in an in- 
verted bottle filled with mercury, it was condenfed into wa- 
ter, without any admixture of air. Indeed, if the odoriferous 
principle in the matter of cancer confift of volatile alkali com- 
bined with animal hepatic air, it could not be expedted that 
it lliould acquire a permanently elaftic form by iimple expofure 
to heat ; becaufe when alkaline and animal hepatic air unite 
together, they form a non-elaftic fubftance that condenfes upon 
the inner furface of the veflel in which they are mixed. 

To difcover whether other animal fubftances yield an aerial 
fluid, fimilar to that which was extricated in the foregoing ex- 
periment from the matter of cancer by means of heat, a portion 
of the fiefh of the neck of a chicken was introduced into a fmail 
coated glafs retort, which was gradually expofed to heat in a fand 
bath till it became red-hot. A thin phlegm, of ay ellowifh colour, 
firft came over : this was foon fucceeded by a yellow empyreu- 
matic oil, and at the fame time a permanently elaftic fluid, having 
an odour refembling that of burned feathers, began to be difen- 
gaged. A flip of paper, tinged with litmus and reddened by ace- 
tous acid, being held over this fluid, became blue. The neck of 
the retort was now introduced below an inverted jar filled with 
mercury, and a confiderable quantity of air, together with a fetid 
empyreumatic oil, were received in the jar. This air was highly 
inflammable : it had a very fetid odour. When a bottle, con- 
taining a portion of it, was agitated with diftilled water, nearly 
one-half of it was abforbed. The refidue was inflammable, and 
burned firft with a flight explofion, and afterwards with a blue 
lambent flame. A little nitrated lilver being dropped into the 
Vol. LXXX. G g g water 


402 Dr. Crawford's ’Experiments on the Matter 

water with which the air had been agitated, the mixture in- 
ftantly acquired a reddifh brown colour ; after fome time it 
became turbid, and a brown precipitate fell to the bottom. 
When two meafures of the air, extricated in this experiment, 
were mixed with one of alkaline air, they occupied the fpace 
of a little more than one meafure and an half. A fecond 
mcafure of alkaline air being added, and the airs being buffered 
to remain together for three days, at the end of that time the 
re fid ue occupied the fpace of two meafures and one-eighth. 
Soon after they were mixed, an oily fluid, of a pale colour, 
was depofited on the internal furface of the jar. At the end 
of the third day this fubftance had acquired a light olive 
colour. It was collected in globules, irregularly diftributed 
over the interior furface of the jar. Thele globules were 
nearly of a folid confiftence. When the jar was removed from 
the mercury, the air contained in it at firft fmelled ftrongly of 
volatile alkali. After a littie time the fined of the alkali 
difappeared, and the odour of empyreumatic oil was difiindtly 
perceived- A fmall quantity of difiilled water, which was 
now agitated in the jar, acquired a brown colour, but did not 
entirely diffolve the vifcid fubftance that adhered to its furface. 
I he water, tnus coloured, was Giviaed into two portions. To 
one of thefe was added a little ftrong vitriolic acid, by which 
the fmell was exalted, and a flight effervefcence was produced. 
Concentrated nitrous acid being added to the other portion, the 
fmell and colour were deftroyed, and a brifk effervefcence took 

place. 

When a portion of the folid fubftance that adhered to the 
interior furface of the jar was feparated, it felt vifcid and 
adhefive between the fingers, and fmelled ftrongly of empy- 
leumatic oil. A little fpirit of wine being introduced into the 

6 i ar » 


of Cancer , and on Animal Hepatic Air . 403 

jar, this vifcid fubftance was difiolved ; the iplrit acquired a 
yellow colour and empyreumatic fmelf, and upon adding to it 
diftilled water the mixture became whitifh and (lightly turbid. 

I next examined the air extricated from putrid veal by diftil- 
lation. A portion of the latter fubftance being introduced into 
a coated glafs retort was expofed to a red heat, and the air 
difengaged was received in a jar over mercury. This aerial 
fluid was found to poflefs nearly the fame properties with that 
which was obtained in the preceding experiments. It was very* 
inflammable ; about one-half of it was foluble in diftilled 
water. The water, thus impregnated, became turbid upon 
the addition of nitrated filver, and a brown precipitate fell to the 
bottom. To another portion of diftilled water iaturated with 
this fluid, dephlogifticated marine acid being added, the fetid 
fmell was deftroyed, a brifk efFervefcence took place, and a 
whitifh gelatinous fubftance was feparated. This fubftance 
being evaporated to drynefs, became black upon the addition of 
concentrated vitriolic acid. When a quantity of the air ob- 
tained in the experiment was agitated with diftilled water until 
no more was abforbed, the refidue took fire upon the applica- 
tion of an ignited body, and burned with a lambent flame. 
It is proper to obferve, that the air extricated from the putrid veal 
had lefs of the empyreumatic fmell than that which was difen- 
gaged from frefh animal fubftances. Its odour indeed was nearly 
fimilar to that of animal fubftances in a ftate of putrefadHon. 

We learn from thefe experiments that the aerial fluids, which 
are extricated from frefh as well as from putrid animal fub- 
ftances by diftillation, have nearly the fame properties with 
that which is difengaged, by a fimilar procefs, from the mat- 
ter of cancer. Each of them appears to confift of two diftmct 
fluids; one of which is foluble, and the other infoluble, in 

G g g 2 water. 


404 Dr. Crawford’s Experiments on the Matter 

water. The portion that is infoluble burns with a lambent 
flame, and has all the chara&ers of heavy inflammable air ; 
whereas the foluble part refembles the fluid which is extricated 
from cancerous matter by the vitriolic acid : it has a fetid odour, 
it decompofes nitrated filver, combines with cauftic volatile 
alkali, and poffefies many of the properties of common hepatic 
air. 

There are feveral particulars, however, in which the animal 
and common hepatic air materially cl i it e r from each other. 
Although they are both fetid, yet their odours are not exaftly 
fimilar. When common hepatic air is decompoled by the con- 
centrated nitrous or dephlogifticated marine acid, iulphur is 
feparated ; but when animal hepatic air is decompoled by thefe 
acids, a white flaky matter is difengaged which is evidently an 
animal fubftance, becaufe it becomes black by the addition of 
concentrated vitriolic acid. Sulphur is moreover leparated 
during the combuftion of common hepatic with atmofpherical 
air; but when the air from animal fubftances is burned with 
atmofpherical air, no precipitation of fulphur takes place. 
Indeed, that animal hepatic air does not contain fulphur will be 
apparent from the following experiment. 

Equal parts of pure air and of air extiicated from frefh beef 
by diftillation, were fired by the eledric fhock in a ftrong glafs 
tube over mercury. A little diftilled water was then introduced 
through the mercury into the tube, and was agitated with the 
air which it contained. A portion of this water being filtered, 
and a fmali quantity of muriated barytes being dropped into it, 
the mixture remained perfectly tranfparent. Hence it appears, 
that the air extricated from frefh beef by diftillation does not 
" contain fulphur ; for, if it had contained that fubftance, the 
fulphur, by its combuftion with the pure air, would have been 
I changed 


of Cancer , and on Animal Hepatic Air . 405 

changed into the vitriolic acid, and the muriated barytes would 
have been decompofed, 

I frequently repeated the preceding experiment with the air 
extricated, by diftillation, from the putrid as well as from the 
frefh mufcular fibres of animals 5 but I could not, in any 
inftance, difcover the leaf!: veftige of the vitriolic acid. 

The following experiments were made with a view more accu- 
rately to analyfe the airs which are difengaged from animal fob- 
ftances by heat, and to determine the products refulting from 
the union of thefe fluids with pure air. 

About an ounce of the lean of frefh mutton was introduced 
into a frnall coated glafs retort, and expofed to a red heat. The 
air that was extricated towards the end of the diftillation was 
received over mercury; and foon after its production, being 
agitated with water, very nearly one half of it was abforbed. 
A fimilar experiment being made with the air difengaged 
towards the middle of the diftillation, the part of it which 
was folublein water was found to be to the part not folublein 
that fluid as 2 to 3. Having buffered a feparate portion of the 
air difengaged towards the end of the diftillation to remain over 
mercury for feven hours, it was found gradually to diminifh ia 
bulk, and a fluid, which had the colour and the odour of a thin 
empyreumatic oil, was collected at the bottom of the jar *. The 
air being now agitated with water, only one-eighth of it was 
abforbed. Hence it appears, that a portion of the air, extri- 
cated from animal fubftances by heat, refembles a fpecies of 
hepatic air which was flrft difcovered by Mr. Kirwan, and 
which exifts in ail -intermediate ftate between the aerial and 
the vaporous ; this fluid not being permanently elaftic like 

* The above-mentioned appearance is not conffant, The air when placed over 
mercury fometimes diminifties, and at other times it retains its oriHnal bulk. • 
have not as yet difcovered the caufe of this difference. 


^o5 ' D/*. Crawford’s Experiments on the Matter 

air, nor immediately condenfed by cold like vapour, but gra- 
dually affuming the non-elaftic foim, in confequence probably 
of the tendency ot its feveral parts to unite witn eacn o^her. 

The air produced in the foregoing experiment rendered lime- 
water turbid ; it therefore contained a quantity of fixed air; 
and towards the end of the diftillation a little volatile alkaline 
air came over, agreeably to the obfervation of M. Berthollet . 
for, when a portion of the air received during this part of the 
procefs was mixed with an equal quantity of marine acid air, a 
white vapour was produced, and a diminution of about one 

twenty-fifth of the whole took place, 

I endeavoured, by the following experiment, to afcertain the 
proportion of fixed air contained in the aerial fluid which is dn- 
enp-aged from the lean of animal fubftances by heat. 

A quantity of air, extricated from the lean of frefh mutton, 
was received over mercury in a large phial which had a narrow 
neck. When the phial was a little more than half filled, the 
remaining portion of the mercury was difplaced by introducing 
water that had been previoufly boiled. The phial being then 
clofely corked, the air and water were brilkly agitated together ; 
and the liquor, thus impregnated with the foluble part of the 
animal air, was put into a proof, to the bottom of which heat 
was applied. By this means a portion of the air was again difen- 
eaged* which was received in a tube inverted over mercury. The 
procefs was continued till the liquor in the proof no longer ren- 
dered lime-water turbid. As the air received in the tube contained 
the fixed air that had been extricated from the liquor, together 
with a quantity of common air expelled from the proof, it was a 

fecond time agitated with water ; and the exaff meafure o t e 

fixed air was known by the portion which the water imbibed. 
The fixed air, thus ascertained, being compared with the entire 
■quantity of air that had been originally abforbed, it appeared 


of Cancer , and on Animal Hepatic Air . 40,7 

that the former was to the latter in bulk as 1 to 4. One-fourth 
therefore of the volume of the foluble part of animal air con- 
fills of fixed air, and the remaining three-fourths of hepatic, 
mixed with a very fmali proportion of alkaline air 

It appeared from the experiment, that animal hepatic air, 
when it was abforbed by water, was not capable of being again, 
difen gaged by a heat which raifed the water to the boiling 
temperature ; for, after the fixed air was expelled, the liquor in 
the proof was made to boil nearly half an hour, but no perma- 
nently elaflic fluid could be difengaged. The portion of the 
liquor which now remained had a faint yellow colour ; it 
fmelled ftrongly of animal hepatic air, and depofited a brown 
precipitate upon the addition of nitrated filver. 

It appears, therefore, that the foluble part of the air which 
is difengaged from the lean of animal fubflances by heat,, con- 
fills of three diftindl fluids; of alkaline air, fixed air, and ani- 
mal hepatic air. It fee me d extremely probable, that thefe 
three aerial fluids, flowly combining together, formed the oily 
empyreumatic fubftance which was colledled at the bottom of 
the jar, while the air was undergoing the diminution defcribed 
above. In this conclufion I was confirmed by trials that were 
made with the empyreumatic oil that came over during the 
latter part of th6 dlflillation : for when it was examined by 
chemical tells, foon after it was obtained, it was found to 
contain fixed air, volatile alkali, and animal hepatic air. 

* It is proper to remark, that, in fome experiments, the relative quantity of 
animal hepatic air was found to be lefs than that which has been hated above. 

I do not as yet know, with certainty, the caufes to which this difference is to be 
attributed ; but I believe it principally depends upon the period of the diftillation 
in which the air is received, the degree of heat applied to the bottom of the retort,, 
and the nature of the animal fubftance employed in the experiment* 


I next 


jc 3 Dr. Crawford’s Experiments on the Matter 

I next endeavoured to determine toe produffs which refult 
from the combuftion of pure air, with animal air, or with the 
compound aerial fluid extricated from the lean of animal fub- 
ftatices by heat. With this intention I expofed the lean of 
frefh mutton, in a fraall coated glals retoit, to a red heat. 
The air which was received over mercury towards the end of 
the diftillation was divided into two feparate portions; one Oi 
which was agitated with water till the foluble part was ab- 
forbed ; the other was not agitated with that fluid. One mea- 
fure of the former was introduced, over mercury, into a ftrong 
,rlafs tube adapted for the purpofe of firing aerial fluids by the 
electric (hock. This was mixed with one meafure and an half 
of pure air. The portion of the tube occupied by the mixture 
was one inch and two-tenths. A fmall (hock being made to 
pafs through it, a violent explofion took place, and the fpace 
occupied by the refidue was nine-tenths of an inch. The 
height of the mercury in the tube, previoufly to the combuftion, 
was 4.8 inches. After the airs were fired, its height was 5.1 
inches. Allowance being made for the difference of expanfion 
produced by this caufe, it appeared, that the volumes of the 
airs, previoufly to the combuftion, and fubfequent to it, were 
as 100 to 75 nearly. The refidue being agitated with water, 
fix-tenths were abforbed ; and the portion which was thus ab- 
forbed was found, by the precipitation which it produced in 
' lime water, to be fixed air. Of the infoluble remainder, five 
parts being mixed with five of nitrous air, a diminution of 
three parts took place ; whence it follows, that one-fifth of 

the infoluble refidue was pure air. 

The pure air which was ufed in this experiment had been 

previoufly agitated with water, to free it entirely from fixed 

a i r and "the, Inflammable air had undergone a fimiiar agitation. 

T f 


of Cancer , and on Animal Hepatic Air . 409 

It is therefore manifeft, that, by the combuftion of the pure 
and inflammable air in the foregoing trial, fixed air was pro* 
duced ; the phlogifticated air, found in the refidue, being that 
which was contained in the pure air before the inflammation 
took place* * 

I next examined the products refulting from the comDuftion 
of pure air with that portion of the animai air which had not 
been previoufly agitated with water. One meafure of this 
fluid, at the expiration of three-fourths of an hour after ic had 
been obtained, was mixed over mercury with one meafure and 
an half of pure air, and fired by the electric fliock. The 
portion of the tube occupied by the mixture, previoufly to the 
deflagration, was one inch and To 5 -© 5 sfter the deflagration, it 
occupied the fpace of one inch and one-tenth. Being agitated 
with lime-water, very nearly one-third was abforbed. A por- 
tion of the infoluble refidue was expofed to a lighted taper, 

and burned with a faint blue flame *• f 

The dephlogifticated air ufed in this experiment had been 
previoufly agitated with water, to free it entirely fiom fixed 
air. It was the pure ft dephlogifticated air I had ever feen : for 
when one meafure of it was mixed with one meafure and 
nine-tenths of nitrous air, the refidue occupied the fpace 01 
only one-fortieth of a meafure. From the foregoing trial it was 
evident, that if parts of pure air were infufficient to faturate 
one of the animal air that had not been previoufly agitated with 
water. The experiment was therefore repeated as follows. I we 

* When I flrfl: made the above experiment, the refldue did not appear to be 
inflammable. It had been tried by applying an inflamed flip of paper to the 
mouth of a phial which was Ailed with it ; but, upon repeating the experiment, 
'when the phial containing the reflduary air was carried into a dark room, and an 
ignited wax taper was applied to its mouth, an evident inflammation took piace. 

Vol, LXXX. H h h .parts 


410 Dr, Crawford’s Experiments on the Matter 

parts of pure air being mixed with one of animal air, occupied .8 
©fan inch. The mixture being fired by the ele&rical fhock, the 
refid ue {food at a little lefs than .5. When this refidue was agi- 
tated with lime-water, it was almoft wholly abforbed. By afub- 
fequent trial it was found, that nearly one-half of the animal 
air ufed in this experiment was foluble in water. 

Hence it appears, that the quantity of pure air required to fa- 
turate the infoluble part of the animal air is fomewhat lefs than 
that required to faturate the compound fluid which had not been 
previoufly agitated with water. But the latter fluid has been 
ihewn to confift almoft entirely of heavy inflammable, animal 
hepatic, and fixed air; and as the laft of thefe is already fatu- 
rated with pure air, it is manifeft, that the above-mentioned 
difference muft depend upon the animal hepatic air. Whence it 
follows, that the latter contains a large portion of the inflam- 
mable principle. From the quantity of fixed air produced in 
the laft of the preceding experiments, there is, moreover, the 
utmoft reafon to believe, that the bafis of heavy inflammable 
forms one of the conftituent parts of animal hepatic air. 

When equal parts of pure and animal air were burned toge- 
ther, a confiderable increaic of bulk almoft invariably took 
place; and when the proportion of the animal was to that of 
pure air as 21 to 15, the bulk of the mixture was increafed 
one half. The air that remained after the combuftion in the 
laft mentioned experiments was inflammable : for a portion of 
it being introduced into a fmall phial, and expofed to a lighted 
candle, it firft exploded, and then burned with a blue lambent 
flame. 

Being defirous of learning the caufe of the increafe of bulk 

in the foregoing experiments, the following trials were made. 

, “ Three 


of Cancer , and on Animal Hepatic Air . 41 c 

Three meafures of animal were mixed with two of pure air, 
and feveral ftrong electrical (hocks were made to pafs through 
the mixture, but it would not take fire. Half a meafure of 
pure air was then added, and the mixture being fired, its bulk 
was encreafed from .9 of an inch to 1 inch and .3. 

Three meafures of this refiduary air were then mixed with 
three of pure air, and fired by the eledric fhock. *1 he bulk of 
the mixture was reduced from 1 inch to .56. This being agi- 
tated with lime-water, twO'thirds were abforbed, and the re- 
mainder confided almoft wholly of pure air* From thefe fads 
it feems probable, that animal hepatic air confifts of a combi- 
nation of heavy and light inflammable air ; and tnat when it 
is fired with a quantity of pure air not fufflcient to faturate it, 
a portion of the animal air is refolved into its elementary prin- 
ciples, in confequence of which its bulk is encreafed. 

It was before obferved, that three parts of animal mixed 
with two of pure air would not take fire. I11 fome ex- 
periments it was found, that when the animal air was 
mixed with a ftill fmaller proportion of pure air, an increafe 
of bulk was produced by the eledric fhock, although no 
deflagration took place ; but when the eledric fhock wa$ 
repeatedly taken through animal air alone , it did not in any 
inftance, as far as I could perceive, produce the fmalleft increafe 
of lize* 

I was next defirous of learning whether an increafe of fize 
would be produced by making the eledric fhock pafs through 
a mixture of pure and alkaline air. Having firft accidentally 
taken two or three fmall fhocks through a little alkaline air, 
and not obferving a fenfible augmentation of bulk, I then 
mixed it with an equal volume of pure air ; and, as I fuppofed 
that no decompofition had taken place, I was not apprehenfive 

H h h 2 of 


412 Dr. Crawford’s Experiments on the Matter 

of an explofion. Contrary, however, to my expedition, the 
airs, when the eleftric fhock was made to pafs through them, 
entered rapidly into an union with each other. The jar which 
I held loofely in my hand, as it was inverted over the mercury, 
was carried obliquely upwards with great violence. Having 
broken the Hand of the prime conductor in its paffage, it 
forced its way through the cylinder of tne electrical machine, 

which it fhivered to a thoufand pieces. 

I afterwards repeated this experiment with a very ftrong 
apparatus, the jar being preffed down by a plate of non, for 
the purpofe of retaining it in its place. 

■■It appeared, that when the alkaline and pure air were imme- 
diately mixed together, and a fmall Ihock was made to pats 
through them, they would not take fire ; but when three or 
four thocks were previoufly taken through the alkaline air, and. 
the latter was afterwards mixed with an equal bulk of pure 
air, they exploded with great violence. The rendue, having 
cooled to the temperature of the furrounding air, was reduced 
to half the original bulk of the mixture. Of this refidue one- 
iixth was undecompofed alkaline air. The remainder wa§- 
phlogifticated air. 

Of the products which refult from the combufiion of fulphureous 

hepatic with pure air. 

The hepatic air employed in the following experiments was, 
procured, agreeably to the method which Mr. Kir wan has 
recommended, by adding marine acid to an artificial combination 
of fulphur and iron. Three meafures of the air thus obtained 
were mixed in a ftrong glafs tube over mercury, with four of 
pure air, and fired by the eledtric fhock.. 


of Cancer, and on Animal Hepatic Air . • 4 a 3 

The pure air was previoufiy agitated with lime-water to free 
it from fixed air, and a portion of the hepatic air, having been 
likewife agitated with lime-water, was found not to occafion 
any precipitation in that fluid. The airs were reduced by the 
explofion to one-fourth of their original bulk. The refidue 
was then transferred over mercury into a (lender graduated 
tube, and diftilled water being admitted, eight-tenths w r ere 
abforbed. To a portion of this water, when filtered, variolated 
filver was added, which inftantly occafioned a copious precipi- 
tate. To a fecond portion was added muriated barytes, which 
occafioned a flight white precipitate not re-diflblvable in a large 
quantity of water; lime-water being added to a third portion, 
did not produce any fenfible precipitation. From the laft fadl 
it does not follow, that no fixed air exifted in the refidue, be- 
caufe the marine acid, which it evidently contained, would 
diffolve the calcareous earth of the lime-water. As a great 
diminution, however, refulted from the combuftion ; and as it 
appeared, from chemical tefts, that the refidue w r as moftly com- 
pofed of marine and vitriolic acid airs, it is manifeft, that, if 
any fixed air was produced, its quantity mu ft have been very 
inconfiderable. 

It has been already obferved, that a flight precipitation took 
place upon the addition of the muriated barytes. The precipi- 
tate was much more confide r able when, mpon repeating the 
experiment, the refidue after the explofion was not tranfi- 
ferred into a graduated tube previoufiy to the admifiion of the 
diftilled water; but the latter was immediately introduced into 
the veflfcl in which the airs were fired. The reafon of this 
difference is evident. The flight, precipitate by . the muriated 
barytes, in the firft inftatice, depended upon the exiftence-of a 
fmall quantity; of variolic acid in an aerial form, or in the 

flats 


Ai 4 Dr. Crawford’s Experiments on the Matter 

ftate of volatile vitriolic acid, which was transferred together 
with the phlogifticated and marine acid air into the fecond 
tube ; but the greater part of the vitriolic acid produced by the 
combuftion adhered, in a fixed ftate, to the furface of the 
tube in which the airs were fired ; and therefore, when th« 
diftilled water was immediately introduced into this tube, a 
copious precipitate was depofited upon the addition of munated 
barytes. 

Hence it appears, that when pure air and fulphureous he- 
patic air, obtained from artificial pyrites by the marine acid, 
are fired together in the above proportions, the produfts are 
fixed vitriolic acid, together with a fmall quantity of the vola- 
tile vitriolic, and marine acids, in an aerial form. The refi- 
due, which the diftilled water did not abforb, was the phlo- 
gifticated air that exifted in the pure air previoufly to the 
combuftion. 

From fublequent trials it appeared, that, when hepatic and 
pure air were fired in equal bulks, the refidue had a ftrong 
odour of volatile vitriolic acid, and moreover contained a fmall 
proportion of undecompofed hepatic air. Thefe fafts feem to 
prove, that the converfion of fulphur into volatile or fixed 
vitriolic acid depends upon the quantity of pure air with which 
it is fupplied. 

The marine acid air, found in this experiment, did not 
appear to form one of the conftituent principles of tne hepatic 
air, but to be merely diffufed through it ; for it was almoft 
wholly feparated, by means of diftilled water, from a different 
portion of the fame air, which was placed in a tube inverted 
over mercury ; the water having a ftronger attraftion to the 

marine acid than to the hepatic air. 

By the following experiment I endeavoured to determine 

whether 


of Cancer , and on Animal Hepatic Air . 4 r 5 

whether vitriolic acid be produced by the combuftion of he- 
patic with atmofpherical air. One meafure of hepatic air, 
obtained from artificial pyrites, was mixed over mercury with 
aoout fix me a fu res of atmofpherical air, and fired by the elec- 
tric (hock. A copious precipitation of fulphur took place, the 
remaining air was then agitated with diftilled water, the latter 
was filtered, and muriated barytes was added, which pro- 
duced a white precipitate not diffoluble in a large quantity of 
water. 

From this, and the foregoing experiment, it appears, that 
when fulphureous hepatic is burned with atmofpherical air, a 
part of the fulphur is changed into vitriolic acid, and the reft 
is precipitated ; but when it is burned with a fufficient quan- 
tity of pure air, the fulphur is wholly converted into vitriolic 
acid. Agreeably to this conclufion, I have found that the 
odour of the volatile vitriolic acid conftantly accompanies the 
combuftion of hepatic with common air in open veflels; and 
that when concentrated nitrous acid is added to water impreg- 
nated with hepatic air, the filtered liquor becomes turbid upon 
the addition of muriated barytes. 

The quantity of pure air required to faturate fulphureous 
hepatic air, does not appear to correfpond with the fuppofition 
that the laft of thefe fluids confifts of fulphur diflolved in 
light inflammable air l for fulphur, in order to its complete 
faturation, requires only 1*43 times its weight of pure air; 
but light inflammable air requires for its faturation at leaft fix 
times its weight of that fluid. The fpecific gravity of hepatic 
air, as determined by Mr. Kirwan, is nearly equal to that of 
pure air. If, therefore, one-fixth of the weight of hepatic 
confifted of light inflammable air, that fluid would require for 
its faturation 2,26 times its bulk of pure air; for the portion 

of 


£ ! 6 Dr. Crawford’s Experiments on the Matter 
of it which con filled of light inflammable air would require a 
quantity of pure air equal in bulk to the hepatic; and the 
remaining portion, confifting of fulphur, would require a 
quantity equal to i .26 of the hepatic. The entire quantity of 
pure air would therefore be to that of the hepatic as 2.20 to r. 

If the hepatic contained one-twelfth of its weight ot light 
inflammable air, it would require for its duration 1.64 ot Us 
bulk of pure air. But from the foregoing experiments it 
appears, that the quantity of pure air, neceflary to faturate one 
meafure of hepatic air, is only 1.33 meafures. Hence it is 
probable, that this fluid does not confift of fulphur diflolvedm 
light inflammable air. 

If we make allowance for the marine acid which was dtf- 
fufed through the hepatic air, it will be found, that the quan- 
ta of pure air required to faturate it is nearly the fame with 
that which would be required to change an equal weight of 
fulphur into vitriolic acid. Whence it may be inferred, agree- 
ably to the opinion of Mr. Kirwan, that hepatic air is fulphur 
which has acquired an aerial form by the application of heat. 
This conclufion is, I think, confirmed by the following expe- 

Tir Tlittle pure fulphur was introduced into an inverted tube, 
which had been previoufly filled with mercury, and the flame 
of a candle was applied to the extremity of the tube. In a 
fhort time a permanently elaftic fluid was produced, which was 
found to have all the charaffers of hepatic air. It is pr a e, 
however, that fome degree of moifture is neceflary to the fuc- 
cefs of this experiment, becaufe the quantity of hepatic air 
which was thus obtained was not very confidence. 

It has been already (hewn, that an oily matter was produce 

by the union between fixed air, volatile alkali, and amma 

J heoatic 


of Cancer , and on Animal H fa tic Air . 4 1 7 

hepatic air. The following experiment proves, that a fub- 
ftance, which has very much the appearance of oil, is formed by 
the combination of fulpbureous hepatic air with fixed air and 
volatile alkali. 

A quantity of impure hepatic air was obtained by adding 
vitriolic acid to common liver of fulphur. When this fluid 
was agitated with lime-water, it produced a copious precipita- 
tion. It therefore contained a confiderable proportion of fixed 
air. One meafure of it was now introduced into a (lender 
graduated tube, inverted over mercury, and was mixed with an 
equal bulk of alkaline air. As foon as the airs came into contaft 
with each other, a white cloud was produced, the mercury 
began gradually to rife in the tube, and at the end of fix hours 
the air that remained occupied the fpace of only one meafure 
and one-third. The furface of the mercury within the tube 
firft became black, and a part of it afterwards acquired a red 
colour refembling cinnabar. In the courfe of the experiment, 
a yellowdfh oleaginous fubftance was depoflted upon the inte* 
rior furface of the tube. This fubftance, in fome parts of the 
furface, formed itfelf into globules ; in others, it was extended 
Into ramifications, having the refemblance of trees in minia- 
ture, and it gradually aflumed a deeper colour, till at length it 
acquired a greenifh caft. The fubftance, thus obtained, had a 
very fetid odour : it appeared to have a near refemblance to an 
animal oil which had become green by putrefadlion. It was, 
however, foluble in water, and the odour of the folution was 
increafed by the vitriolic, and deftroyed by the concentrated 
nitrous and dephlogifticated marine acids. 

Mr. Cruikshank, who affifted me in moft of the fore- 
going experiments, and on whofe accuracy 1 could place the 
greateft reliance, examined, in my abfence, the red and black 
Vo l. LXXX. I i i powders 


4i 8 Dr. Crawford’s Experiments on the Matter 
powders which were formed by the aaion of the hepatic air 
upon the furface of the mercury, and found them to be aethiops 

mineral, and cinnabar. 

Of the air extricated from animal fubftances by putrefaction. 

In the beginning of July, 1789, about two ounces of veal, 
{lightly putrid, was introduced into a large phial, which was 
filled with diftilled water, and inverted over a quantity of 
the fame fluid. At the end of three days a few bubbles of air 
had appeared at the bottom of the phial; the water had ac- 
quired a light brown colour, and emitted a fetid fmell. At the 
expiration of feven days we could perceive that the quantity of 
air at the bottom of the phial was manifeftly increafed, al- 
though its progrefs was very flow. The water, by the diflolutioii 
of a part of the veal, had now acquired the confidence of a 
thin mucus, its brown colour was fomewhat deepened, and it 
emitted a highly fetid fmell. A little nitrated filver being 
dropped into a portion of this water, previoufly filtered, a daik 
brown precipitate was immediately produced. Lime-water, 
mixed with another portion of it, occasioned an afh-coloured 
precipitate ; and when concentrated nitrous acid was added to a 
third portion, the fetid fmell was deftroyed, a flight efier- 
vefcence took place, and a yellow flaky matter was difengaged. 
At the end of feven weeks, a quantity of air, amounting to 
two and one-fixth dram meafures was collected in the phial. 
This air had a fetid odour. Being agitated with water, fix- 
tenths of it was abforbed. The refidue extinguifhed flame. 

I next examined the air extricated from veal which was fuf- 
fered to putrefy over mercury. 

Oa 


of CancW, and on Animal Hepatic Air* 4 l 9 

On the 28th of July, 1789, two drams and twenty-four 
grains of the lean of frefh veal was introduced into a narrow 
jar, which was filled with mercury, and inverted over that 
fluid. At the end of eight days the air, which was (lowly extri- 
cated, had communicated a brown colour to the furface of the 
mercury* On the 13th of September* the quantity of air difen- 
gaged was a little more than two ounce meafures. This fluid 
had a very fetid fmell. Two feparate portions of diftilled water 
being faturated with it, the firft, upon the addition of nitrated 
iilver, depofited a brown precipitate; and the laft, when it 
was mixed with lime-water, produced a brown ifh a(h-coloured 
cloud. A third portion of the air being ftrongly agitated with 
diftilled water, was reduced to one-fixteenth of its. original 
bulk. The refidue extinguifhed flame. 

The veal which had remained fo long in contact with the 
mercury had not loft its firm texture* Its fmell was putrid # 
but not very offenfive. 

The quantity of elaftic fluid collected in this experiment 
was much greater than in the preceding one ; becaufe in the pre- 
ceding experiment, although the putrefaction advanced more 
rapidly, yet the fixed and hepatic air were abforbed by the 
water nearly as faft as they were difengaged from the putrid 
fubftance. 

Hence it appears* that the aerial fluids, which are extricated 
from the mufcular fibres of animals by putrefaction, confift of 
fixed and animal hepatic, mixed with a very fmall proportion 
of phlogifticated air 


* It may be proper to remark, that 1 have obtained, by diftillation from the 
green leaves of a cabbage* an aerial fluid, which, in molt of its properties. 


refembles animal hepatic air. 



I . • 

1 1 2 


420 


Dr. Crawford’s Experiments on the Matter 


Of the effects produced ly expofing frefi animal fubjlances to 

atmofpherical, hepatic , and pure air. 

Two tubes, of nearly the fame fize, were inverted over 
mercury. Into one of thefe was introduced common air, and 
into the other an equal bulk of hepatic air, obtained from liver 
of fulphur by the vitriolic acid. Equal quantities of frefli 
veal, confiding of a mixture of mufcular fibres and of fat, 
and weighing each one dram, were then expoled to thefe airs. 
At the end of three days the piece that was in contact with the 
common air had not altered its colour or confidence, but 
fmelled a little putrid. The colour of the fatty parts of the 
piece that was expofed to the hepatic air was changed to a dark 
green, the mufcular fibres were cracked and fhrivelled on the 
furface as if they had been feared with a hot iron, and the 
whole had acquired a foft confidence. 

Similar trials were made with two pieces of frefh veal, one 
of which was expofed' over mercury to common air, and the 
other to air extricated from putrid veal by didillation. The 
former in three days had not changed its appearance ; the latter 
had become green round the edges, and was interfperfed with 
green fpots. The furface of the mercury in the jar which 
contained the lad had acquired a brown colour ; whereas that 
of the mercury in the jar which contained the common air was 
clear and bright. The pieces of veal were differed to remain 
in this fituation for fix weeks. After a few days had expired, 
that which was expofed to the animal air did not appear to 
differ any farther change. Its colour, which in the courfe of 
a week had become brown, continued unaltered, and no difio- 
iution took place. The air at the lad was very fetid ; it occar 

fioned 


ef Cancer , and on Animal Hepatic Air. 421 

fioned a copious precipitate in lime-water ; it was highly in- 
flammable, and burned with a blue lambent flame. 

The piece, on the contrary, which was expofed to the com- 
mon air, did not, as has been already obferved, fo foon lofe its 
fibrous texture, nor fo y fpeedily acquire a dark colour, as that 
which was in contadt with the animal air. But the progrefs 
of its putrefaction did not appear to flop at the end of a few 
days, as in the latter inftance. It advanced flowly, and at the 
expiration of fix weeks a confiderable part of the rnufcular 
fibres had run down to a brown liquid. The air in which it 
was placed now occafioned a copious precipitation in lime- 
water, and the brown liquid was found to be impregnated with 
animal hepatic and fixed air ; the exiftence of the latter being 
known by means of lime-water, and that of the former by 
its occafioning a dark precipitate in a folution of nitrated filver, 
as well as by its fetid odour, which was increafed by the vitri- 
olic, and defcroyed by the concentrated nitrous and dephlogifti- 
cated marine acids* 

The following experiment was made with a view to deter- 
mine whether pure air accelerates the progrefs of putrefadtion> 
in animal fubftances. , 

In the month of December, 1789, equal portions of pure 
and of common air were introduced into two equal jars over 
mercury, in each of which was placed about two drams of 
frefh beef. At the end of a week, the beef which was expofed to 
the pure air had become highly putrid ;, but very little change 
was produced in that which was expofed to the common air. 

The fadts which have been afcertained by the preceding 
experiments, appear to lead to the following conclufions refpedt- 
ing the procefs of putrefadtion in the lean of animal fub- 
ftances. 

6 , 


The 


422 Dr. Crawford’s Experiments on the Matte) 

The mufcular fibres of animals contain fixed and phiogiln- 
cated air, the inflammable principle in the ftate of heavy and 
of light inflammable air, and a fubflance which, by means or 
heat or of putrefaction, is capable of being converted into 
animal hepatic air*. When the mufcular fibre, after the 
death of the animal, is expofed to the pure air of the atmo- 
fphere; the latter, by a fuperior attraction, combining with the 
heavy inflammable air, produces fixed air, and at the lame time 
furnilhes' the quantity of heat necefl'ary to the formation ot 
animal hepatic air. The cohefion of the fibre being thus de- 
frayed, the fixed, as well as the light inflammable and phlo- 
gifticated air, which enter into its compofition, are difengaged, 
and the two latter fluids uniting with each other produce the 

volatile alkali. _ _ . 

The alterations which take place in putrefaction are in molt 

refpeCts fimilar to thofe which arife from deftruthve diftilla- 
tion. By expofure to heat the fixed air of the animal fibre is 
extricated, hepatic air and volatile alkali are produced, and the 
inflammable principle not coming into contaCt with the pure 
' air of the atmofphere, is raifed in the form of heavy inflam- 

mable air. ... * 

1 have found, that the fetid odour of animal hepatic air is 

defrayed by mixing it with pure air, and fullering it to i^.main 
in contadt with that fluid for feveral weeks. ^ hen it was 
placed in this fituation, it acquired an odour which was not 
exactly fimilar to any that I had ever before perceived, but 
which bore feme refemblance to that of inflammable air ob- 
tained by diflolving iron in fpirit of vitriol. 

* It is fcarcely neceffary to obferve, that the exiftence of fixed, inflammable, 
and phlogifticated air in animal fubftances, and the eompofition of volatile alka >, 
were difeovered before I began to give particular attention to this fubjedh ^ 


of Cancer , and on Animal Hepatic Air „ 423 

The peculiar fmell of animal hepatic air is likewife de- 
ft royed by agitating it with vinegar, or with the concentrated 
vitriolic acid. But the fluids which moft fpeedily produce this 
effedt, are the concentrated nitrous and dephlogifticated marine 
acids; and thefe fluids are known to abound with pure air. It is 
therefore extremely probable, that this alteration depends upon 
an union between the pure air of the latter fubftances and the 
animal hepatic air, or fome of its conftituent parts. 

It appears from the experiments which have been recited 
above, that in cancerous and other malignant ulcers, the ani- 
mal fibres undergo nearly the fame changes which are produced 
in them by putrefadtion, or by deftrudtive diftillation. The 
purulent matter prepared for the purpofe of healing the ulcer 
is, in fuch cafes, mixed with animal hepatic air and volatile 
alkali. The compound formed by the union of thefe fub- 
ftances, which may perhaps not improperly be termed hepa- 
tifed ammonia, decompofes metallic falts, and adts upon me- 
tals : for we have feen, that when it was placed in ajar over 
mercury for feveral days, the fur face of the mercury acquired 
a black colour ; and that it inftantly occafioned a dark precipi- 
tate in a folution of nitrated filver. Thefe fadls feem to afford 
an explanation of the changes produced in metallic falts, when 
they are applied to malignant ulcers. The volatile alkali com- 
bines with the acid of the metallic fait, and the animal hepa- 
tic air revives the metal, either by imparting to it the inflam- 
mable principle, or by uniting with the pure air which the 
calx is fuppofed to contain. The metal, thus revived, is pro- 
bably in fome cafes again corroded by the hepatifed ammonia, 
which communicates to it a black colour. Thus we may 
account for the dark ingruftation frequently formed upon the 

tongue 


Dr. Crawford’s Experiments on the Matter 

tongue and internal fauces, when venereal ulcers of the throat 
are waffled with a folution of corrofive fublimate. And hence 
alfo the dark tinge which is frequently communicated by ill- 
conditioned ulcers to poultices made with a folution of fugar of 
lead. The a&ion of the hepatifed ammonia likewife explains 
the reafon why the probes are frequently corroded when they 
are introduced into finuous ulcers, or applied to the furfaces of 
carious bones. To the fame caufe it is probably owing, that 
polilhed metallic veflels are quickly tarnilhed, when they are 
expofed to the effluvia of putrid animal fubftances. 

From the foregoing experiments it moreover appeals, that 
animal hepatic air imparts to the fat of animals recently killed 
a green colour ; that it renders the mufcular fibres iott and 
flaccid, and increafes the tendency to putrefaction. It is there' 
fore a feptic principle ; and hence it is extremely probable, that 
the compound of this fluid with volatile alkali, which is found 
in the matter difeharged by the open cancer, produces dele- 
terious effects : for although the mifehief in cancerous ulcers 
feems principally to depend upon a morbid action of the vef- 
fels, whence the unhealthy ftate of the matter difeharged by 
fuch ulcers is fuppofed to derive its origin, yet from the cor- 
rofion of the coats of the larger blood-vefiels, and the obftruc- 
tions in the contiguous glands, there can be little doubt that 
this matter aggravates the difeafe. The experiments recited 
above appear to prove, that the hepatifed ammonia is the in- 
gredient which communicates to the cancerous matter its putrid 
fmell, its greater thinnefs, and, in a word, all the peculiar 

.properties by which it differs from healthy pus. 

From thefe confiderations it was inferred, that a medicine 
which would decompofe the hepatifed ammonia, and deflroy 

the fetor of the animal hepatic air, without at the fame tune 

increafing 


of Cancer , and on Animal Hepatic Air . 425 

increafing the morbid adlion of the veffels, would be produdtive 
of falutary effects. The nitrous acid does not deftroy the fetor 
of hepatic air, unlefs it be highly concentrated ; and in this 
ftate it is well known that it fpeedily corrodes animal fub- 
ftances. But the fetor of hepatic air quickly difappears when 
it is mixed with the dephlogiflicated marine acid, even though 
the latter be fo much diluted with water as to render it a very 
mild application. 1 have found that this acid, diluted with 
thrice its weight of water, gives but little pain when it is 
applied to ulcers that are not very irritable; and in feveral 
cafes of cancer it appeared to corredt the fetor, and to produce 
a thicker and more healthy pus. It is proper, however, to 
remark, that other cafes occurred in which it did not feem to 
be attended with the fame falutary effedts. Indeed, fome can- 
cerous ulcers are fo extremely irritable, that applications which 
are at all of a ftimulating nature cannot be ventured upon with 
fafety. And hence if the obfervations, which I have made on 
the efficacy of this acid as an external application, fhould be 
confirmed by future experience, it miift be left to the judge- 
ment of the furgeon to determine both the degree of its dilution, 
and the cafes in which it may be employed with advantage. 

The dephlogifticated marine acid, as is generally known, 
has the power of deftroying the colour, the fmell, and per- 
haps the tafte, of the greater part of animal and vegetable 
fubftances. We have feen that it corredls the fetor of putrid 
fleffi. And I have found, that, when it is poured in fufficient 
quantity upon hemlock and opium, thefe narcotics fpeedily 
lofe their fenfible qualities. As it appears, therefore, to poffefs 
the power of corredting the vegetable, and probably many of 
the animal poifons, it feemed not unlikely, that it might be 
ufeful as an internal medicine. Conceiving that its exhibition 
Vo l. LXXX. K k k would 


2 g Dr. Crawford’s Experiments , &c. 

Jould be perfectly fafe, I once took twenty drops of It diluted 
with water, I foon afterwards, however, felt an obtufe pain, 
•with a fenfe of conftriction, in my ftomach and bowels. This 
uneafmefs, notwithftanding the ufe of emetics and laxatives, 
lafted for feveral days, and was at length removed by drinking 
water impregnated with fulphureous hepatic air. 1 afterwards 
found, that Ae manganefe, which had been ufed in the diftilla- 
tion of the acid, contained a fmall portion of lead. 

Dr.lNGEN-Housz informed me, that a Dutchman of hisac- 
quaintance, fome time ago, drank a confiderable quantity of 
the dephlogifticated marine acid : the effects which it produced 
were l'o extremely violent, that he narrowly efcaped with his 
life If therefore this acid fhould hereafter be employed as an 
internal medicine, it would be neceffary to prepare it by means 
of manganefe that has been previoufly feparated, by a che- 
mical procefs, from the lead and the other metals with which 
that fubftance is ufually contaminated. 





•V 




C 427 J 


XXIII. On the Satellites of the Planet Saturn , and the Rotation 
of its Ring on an Axis* By William Herfchel, LL,D* 
F. R. S. 


Read June 17, 1790. 

I N fny laft Paper on the Planet Saturn, the principal objed 
of which was to give an immediate account of the 
mo ft interefting phenomena that had occurred till the begin- 
ning of November, many things were left unnoticed for want 
of time to treat of them with fufficient. accuracy; but having 
now before me the whole feries of obfervations from the 18th 
of July till the 25th of December, 1789, I can enter into a 
proper examination, affifted by fuch neceflary calculations as 

then could not conveniently be made. 

One of the principal motives which have induced me to 
haften this inquiry, is the frequent appearance of protuberant 
and lucid points on the arms of the ring of Saturn. I have 
mentioned before that fuch phenomena had been refolved by 
the fituation of fatellites that put on thefe appearances ; but as 
my obfervations were continued near two months afterwards, 
and as I had from them correded the epochae of the old fatel- 
lites, and improved the tables of the new ones, I found that, 
befides many of thefe bright points which were completely 
accounted for by the calculated places of the fatellites, there 
were alfo many more mentioned in my journal that would not 

accord with the fituation of any of them. 

> K k k 2 


The 


• 2 g £)r. Herschel’s Obfervatlons on the 

The qu eft ion then prefented itfelf very naturally, what to 
make of thefe protuberant points? To admit two or three 
more fatellites by way of folving fuch phaenomena appeared to 
me too hazardous an hypothefis ; etpecially as thefe lucid 
points, though fome of them had a motion, did not leem 
willing to conform to the criterion I had before ufed of coming 
off the ring, and {hewing themfelves as la..ellites. Ann yet a 
fufpicion of at leaft one more fateilite would often return ; it 
was even confiderably ftrengthened when I dilcovered, by 
means of re-calculating with great precifion the whole leries of 
obfervations, that in the beginning of the featon there had 
been fome few miftakes in the names of the fatellites, when 
the obfervations of them were entered in the journal. In 
fetting them right, which threw a great light upon the revolu- 
tion of the 6th, and more efpecially upon that of the 7th, I 
found alfo, that fome of the obfervations which were entered 
by the name of the 7th fateilite could not belong to that, nor 
to any other known one. It remained therefore to be examined 
whether there might not be fufficient ground to fufpedt the 
exiftence of an eighth fateilite. 

In this fituation of things, I thought it moft advifable to 
draw out the whole feries of obfervations in a paper, beginning 
at the 5th fateilite, and thus gradually through the 4th, 3d, 
2d, 1 ft, 6th, and 7th, to approach towards the center of Sa- 
turn ; that it might appear at laft what obfervations were left 
■unaccounted for. By this means alfo it will be feen clearly 
with how fcrupulous an attention the identity of every fateilite 
has been afcertained; and with a view to give the ftrongeft 
fatisfa&ion in this refpedt, at leaf!; one obfervation of each has 

been calculated for each night ; and the place thus computed is 

put 


Satellites of the Planet Saturn . 429 

put down in the notes, that it may be compared with the 
obferved one. 

To facilitate this comparifon, I have delineated a fcheme 
wherein the orbits of the iatellites are drawn in their due pro- 
portion. A few words will explain the conftruftion and ufe of 
this figure, which, notwithftanding its fimplicity, is yet amply 
fufficient to afcertain the accuracy of every obfervation. 

In each of the orbits, by way of marking them, is placed 
the fateliite to which it belongs, as it appeared to be fituated 
the 1 8th of October, 1789. The graduated circle is of ufe to 
find, by means of the tables, the apparent place of a fateliite 
for any given time ; or, the apparent lituation of the fame 
fateliite being given, its real Saturnicentric place may be de- 
duced from it. In the center of the fcheme is the planet Sa- 
turn, and its ring, exprelied by a line which reprefents the 
direction of its an fie ; or the ring itfelf, as it appeared in my 
telefcopes during the months of July, Auguft, September, 
Q&ober, and November, 1789. The five lines which are 
carried on parallel to each other ferve to convey the meafure 
of the planet, and its ring, to the orbits, of the fatellites, as 
will be feen in feveral inftances that occur hereafter. 

The graduated circle is divided into degrees, and begins to 
count from that part of every fatellite’s orbit beyond the pla- 
net, which is intercepted by a plane palling from the eye of 
the obferver, at redlangles to the ring, through the center of 
Saturn. Hence it follows, that the point of zero, or 360 de- 
grees, is the fame with the geocentric place of the planet in 
thofe four parts of the orbit of the fateliite where the eye 
is in the plane of the ring, and where it appears the moll 
open ; and that, in other places, it may be had by folving one 
fpherical triangle. This is to be underftood as relating only to 

* See Tab. XIX. fig. 1. 


the 


/ 


Dr. Herschel’s Obfervatiohs on the 
the inner fatellites; the 5th, or outermoft, requiring a dif- 
ferent reduction, on account of its deviation from the plane of 
the ring. Moreover, I am inclined to believe, that tne lureft 
way of obferving the 5th, is to truft only to meafures, taken 
with micrometers which give the diftance and angle of por- 
tion, except in fuch cafes when the eye is nearly in tne plane 
of this fatellite’s orbit, where the different reductions may be 
negtedted, without bringing on any conliderable inaccuracies. 
The order of the numbers by which 90 comes to tne left, and 
270 to the right, is taken from the motion ot the fatellites, 
as they appear to revolve in their orbits, when feen 111 tele- 
fcopes of my conftruction ; and which is alfo the real direction 
of their motion according to the order of the figns. but the 
points 360 and 1S0 mult occafionally be changed in their de- 
nomination of north or fouth, according to the real fituation 
of the plane of each fatellite’s orbit. At prefent, for inftance, 
when the fatellites are at 360, that part of their oibits in 
which we find them lies to the fouth of the center of the 
planet; but about the end of Auguft, 1789, and afterwards, 
the orbits of the fix inner fatellites were differently fituated ; fo 
that the fame points then were turned towards the north. I 
need not remark, that the fituation of thefe points was 
changed again when the earth palfed through the plane of the 
ring, and that it will change, in the 5th fatellite likewife, 
when we come to be in the plane of its orbit. 

The calculations of the places of all the fatellites have been 

made according to tables which are given at the end of this 

Paper. Their form being very Ample, I thought it not amifs 

to communicate them, for the ufe of thofe who may with to 

enter into a more particular examination of the following ob« 

fer vat 10ns % or to follow the fatellites in their orbits at an^ 

future 


1 


Satellites of the Planet Saturn . i 

future time. It will be proper to mention, that I have deduced 
the epochae of all the feven fatellites from my own obferva- 
tions, and they will be found to differ confiderably from thofe 
which are given by M. de la Lande, in the Connoljfance des 
Temps for 1 791. But I have not attempted to extend them 
farther than a few years backwards or forwards, as I am not in 
poflefiion of any obfervations that could authorize me to under- 
take fuch a work. On the contrary, I am well convinced, 
that no tables will give us the fituation of the fatellites accu- 
rately, till we have at lead: eftablifhed the dimenfions of their 
elliptical orbits, and the motion as well as the fituation of their 
aphelia. The epochae for 1789, therefore* mud: be looked 
upon not as mean ones, but fuch as refpeCt the orbits of thefe 
fatellites in their fituation during the time of the following 
obfervations ; and the two preceding, and two following years* 
mud: be already a little affeCted with thofe errors which are 
the neceffary confequence of our not knowing the required 
elements. I flatter myfelf, however, that the obfervations, 
which are delivered in this Paper, will ferve as a beginning to 
a proper foundation for inveftigating them. The many con- 
junctions between the fatellites, for indance, will undoubtedly 
throw fome light on the fituation and excentricitv of their 
orbits ; as it will be found, that the calculated places of thefe 
conjunctions require elliptical motions to bring the fatellites to 
fuch appearances, which, in circular orbits, could not fo accu- 
rately have taken place. Nor can we afcribe the difagreements 
to the fault of the obfervations, iince a very few minutes will 
fuffice to determine the time of a conjunction, which never 
lads long. For this reafon alfo, I have carefully avoided de- 
ducing my epochae from conjunctions, even with the 6th 

fatellite, 


^2 Dr. Herschel’s Obfervations on the 

fatellite, which moves fo rapidly that, at firft light, we might 

think thole fituations favourable. 

The mean motion of the five old fatellites, as being Suffi- 
ciently accurate for my prefent purpofe, I have taken from 
the above-mentioned tables of M. de la Lande; and thofe 
of the 6th and yth, of courfe, are the relult ot my own 

obfervations. . 

The geocentric place of Saturn, whofe complement is to be 

added, in order to reduce the Saturnicentric iituation of the 
fatellites to the apparent one, I have taken from the nautical 
almanac to the neareft minute ; and, as 1 have always con ne 
myfelf to a literal tranfcription of the obfervations from the 
original journal, all the memorandums which are neceffary 
either to explain them, or to correft miftakes in the names of 
the fatellites, are thrown into notes, that there may be no inter- 
ruption in the fucceffion of the obfervations. 

Obfervations on the fifth fatellite of Saturn. 

1789’ July 18. 20 h. 20' (A). The fuppofed fifth fatel- 
lite (B) 6° or 7 0 f P . (C) the ring (D). Ju , y 

, A) The time of my obfervations being fidereal, it is neceffary to mention, 
that this relates only to the hours, minutes, and feconds, the day itfelf being 
that which is generally ufed by ahronomers, beginning at noon, and ending I he 
. noon following. By this means there can never be a m.ftake whtch ftdereal hou 
I mean to point out, as no two fuch hours can occur in the fame aftronom.cal 

"twill alfo be neceffary to remark, that all the times are thofe (hewn by the 
clock ; which, by equal altitudes, has been found to lofe very equally at the ra 
of o" 4 Per day ; and to be 8' 51 ", 5 too faff at midnight the iSth ot Joiy, 
i 7 8 9 , which is the time on which my obfervattons on Saturn commenced 

fB The fatellite itfelf not being known, it is here called the fuppofed fifth. 
(C) By fix or fovea degrees fouth preceding the line of the ring, is mean^. 


433 


Satellites of the Planet Saturn . 

July 23. 19 29. The 5th fp. at a great diftance (E). 

July 28. 22 37. By a figure in the journal, at a grekt diftance 

op- ( F > 

Aug. 18. 2i 11. The fuppofed 5th at a great diftance 25° 

up. R. (G). 

Aug. 28. 1 28. A line drawn through a large ftar north of 
Saturn, and palling between one pretty confiderable ftar n£ 
and another ff. Saturn, leaves the fuppofed 5th fatellite a little 
on the following fide. By two figures in the journal, the 5th 
is at a great diftance nf. f? . (H). 

Aug. 29. 23 29. The fuppofed 5th is a very little preceding 
a line drawn from the large ftar of laft night, through a very 
fmall ftar ; and a good deal following a line drawn from the 

that the fatellite in the firft place was at the preceding fide of the planet ; that is, 
in the femicircle from 180 to 360, which paffes through 270 degrees. And in 
the next, that the fituation of its orbit was fuch as to bring the fatellite, at its 
proper diftance, into a line drawn from the center of Saturn, making an angle 
of 6 or 7 degrees with the line of the ring, and declining towards the fouth. 

(D) The calculated place for 20 h. 20', Ihewn by the clock, corre£led by 
— 8' 51", 5, and reduced to iah. 22' 16" mean time, is 245°,$ which, as no 
diftance is mentioned, leaves it doubtful whether the obfervation was that of the 
5th fatellite, or of a fixed ftar. 

(E) By calculation the fituation is 268°,i; which agrees well enough for 
2lh. II' 47" mean time. 

(F) 13 h. 59' 38" mean time gives 291 °,S» which agrees with the diftance 
and direction ; but as the fatellite was fp. the obfervation, which fays np. mull 
belong to fome fmall fixed ftar. 

(G) The calculation for 11 h. n' 27" gives 27 °j 4 or at a g 00 ^ diftance ff ; 
therefore this was not the fatellite, but a ftar. 

(H) It appears from the calculation for 14 h. 48' 29^ which gives 74 °> 2 > an( * 
alfo from the following obfervations, that this was the real 5th fatellite * and 
that, having once obtained its place, I kept it in view all the reft of the feafon. 

Vol. LXXX. L 1 1 - • firft 


434 


Dr . Herschel’s Obfervatiom on the 


fir ft pretty confiderable ftar of laft night, through the fame 
very fmall ftar (I). 

Aug. 3 t . 21 3. The 5th I take to be nf. ^ at a good dis- 
tance (K), 

Sept. 8. 22 37. The 5th about 15 0 nf. R. and, by a figure, 
at a great diftance (L). 

Sept. 11. 20 11. The fuppofed 5th Satellite and two fmall 
ftars ff. a ftar x 9 which is ff. \ , form an exact line. 

22 32. The fuppofed 5th, and the two S ft. ff. form no 
longer a line ; fo that is the real fifth Satellite. 

Sept. 11. 23 52. The 3th Satellite keeps advancing; its 
Situation is 20 or 22 0 nf. the line of the R. and, by a figure, 
it is at a confiderable diftance (M). 

Sept. 13. 22 1 7. The 5th fat. of the nth of Sept, is ad- 
vanced, and is now north preceding a confiderable large ftar, 
which was that night fp. . By a figure it is nf. i? , at a 
confiderable diftance (N). 

Sept 14. 20 33. The 5th a little nearer than laft night (O). 

22 30. The 5th fat. of Sept. 11. obferved at 20 h. 1 1 / , has 
left the place where it was at that time. 

-Sept. 16. 1939. The 5th is drawing nearer towards its 
conjunction. 

22 18. Much the fame as before. 

2 3 59* About 33 0 north following the direction of the 


R. (P). 


1 3. The 5th nearly as before. 


(I) 12 45 53- 78,4* ' 

(L) 11 14 47. 124,2. (M) 

(N T ) 10 35 13. 147,2. (O) 

f?) 12 5 9. 161,3. 


(M) 12 17 48. 138,3. 

(°) 8 47 34* 15 h 5* 



Sept* 


Satellites of the Planet Saturn . 4^5 

Sept. 17. 19 48. The 5th fat, of \ 30° nf. R. and at the 
diftance of about 3 dia. of R. (Q). 

Sept. 1 8. 21 15. About 2 dia. of R. and near 40° north 
following (R). 

Sept. 20. 23 24. The 5th fat. is within a degree of its con- 
junction. It is north of ip , and its motion is retrograde, 

23 54. A perpendicular from the 5th fat. to the ring of 
Saturn, falls towards the following iide flVort of the center by 
4 dia. of Tp . 

0 19. Diftance of the 5th fateilite from the parallel of the 
R. of ^ , 3 rev. 36,7 parts = T c >",966 central meafure. 

1 25. The 5th very nearly central. 

1 28. With a power of 240, perfectly central. With 200. 
perfectly central (S). 

Sept. 21. 21 15. The 5th fat. is perpendicular to a place 
half a projection of the ring preceding the edge of it (T). 

Sept. 23. 22 31. At a confiderable diftance np. ip (Vj. 

Sept. 24. 19 56. At a good diftance np. ip (W). 

Sept. 25. 19 34._The 5th purfues its track (X). 

1 v v 

ii. n u o h » 

(Q) 7 5° 55- 165,1. (R) 9 13 45. 1 70,0. 

(S) 13 18 13, 180,0, or dire&Iy at reftangles to the ring, to the north* 

I have ufed this obfervation for fettling the epocha of this fateilite, in which I 
have made no other allowance than that of the geocentric place of Saturn, as I 
knew this would anfwer all my purpofes. But when we would obtain the mean 
motion of this fateilite in comparing its prefent place with other fituations at a 
great diftance of time, proper redudions of the geocentric place of J? to the 
orbit of this fateilite fhould be made. This may, however, be done much better 
when the real fituation of its orbit is properly afcertained. 

k* / // o h, / u 0 

(T) 9 1 59. 183,8. (V) 10 29 52. i 93 9 ? 3 « 

(W) 7 31 25. 197,4. (X) 7 533. 201,9. 

L 1 1 2 OCt, 


4^6 Dr. Herschel’s Obfervations on the 

061 . 12. 21 18. The fuppofed 5th forms nearly an ifofceles 
triangle with two preceding ftars, the fouthern one of which 
is double, confining of a very confiderable ftar and a ftnall one. 
By a figure, at a confiderable difiance, np. t? (Y). 

061 . 15. 21 1. The large ftar of the double ftar in the 
figure of the 12th of 061 . is gone from its place, and the fup- 
pofed 5th of that night is left (Z). 

2 1 8. The real 5th is fo bright this evening, and was fo the 

i2th of 061 . that I miftook it on that account for a confidera- 

ble ftar 5 it was then nf. b . By three figures to-night it is 
at a great diftance np. t? . I faw it move to-night ; for at 
21 h. i 7 it made an angle of 50° on the following fide with 

three ftars in a line, fp. b . At 1 h. 9', that angle was lefts 

than 40° ; and at 1 h. 4ft, it was no more than about 35 0 . 

061 . 16. 20 16. The 5th now precedes a line drawn through 
the three ftars which it followed laft night at 21 h. T. By 
five figures, at a great diftance fp. t? (A). 

06 t. 18. 20 1 8. At a great diftance fp. 

21 51. At 7 or 8' diftance fp. The fame by two 
figures (B). 

061 . 20. 20 50. By three figures, at a great diftance fp. (C). 

06 t. 28. 21 1. The 5th about 3I dia. of b diftant, and 

45° f P- ( D > 

Oft. 29. 21 49. The 5th fat. of 17 is approaching towards 
its oppoiition (E). 

(Y) 7 li. 42' 32". 280°, 3. The diftance and fituation agree well enough, 

but not the angle, which, by what will appear hereafter from the fituation of the 
modes of this fatellite, Ihould be fp. 

(Z) 7 13 49. 294,0. 

(B) 7 5 1 54 - 3 ° 7 > 9 - 

(D) 6 22 47, 353,4. 


n 


h, 

(A) 6 25 o. 
(C) 6 43 13. 
(E) 7 6 44 * 


298,4. 

3l6,8. 

358 , 1 . 


061 . 


Satellites of the Planet Saturn . 


4 


0 <ft. 30. 20 53. The 5th fat. is paft the oppofition a little 
more than yefterday it wanted of it (F). 

0£t. 31. 21 13. The 5th about 3I diameters of Saturn 
ff. (G). 

21 43. It is very faint; fainter than the firft ; not much 
brighter than the fixth (H). 

Nov. 2. 23 57. By a figure, the 5th fat. at fome diftance 


Nov. 3. 22 1. At a good diftance ff. R* (K). 

22 13. The 5th a little following a line drawn through two 
fixed ftars and between them. It is fouth of the ring. 

Nov. 4. 22 17. The 5th at a great diftance following, and 
a very little fouth ; it precedes the line of the two ftars which 
it followed laft night (L). 

Nov. 7. 22 9. The 5th at a great diftance following, and a 

little north (M). , 

Nov. 8. 20 46. At a great diftance following (N). 

Nov. 10. 23 30. As the calculation gives it (O). 

(F) 6h. 6' 57". 2°,5. (G) 6 h. 22' 59". f> 1 - 

(H) From the conliderable change in the light of this fatellite, we may 
furmife, that it has a revolution upon its axis ; the fituation (fee note Z and G), 
which affe&s the apparent brightnefs, Ihould however be taken into the account® 

(I) 8 h. 58' 41". i6°,8. (K) 6 h. 59' 4?\ 2i°,o. 

(L) 7 h. u'6". 2 5 0 , 2. A few days ago I perceived, that in the former 

part of thefe obfervations I had omitted a pretty eflential circumftance, which is 
an attention to the nodes of the 5th fat. with the ring of Saturn. 

(M) 6 h. 51' 2 1 ". 39 0 , 2. It appears from this and the foregoing obferva- 

tion, that the afcending node of the 5th fatellite, with regard to the ring of Sa- 
turn, apparently lies between the 25th and 39th degrees, which, reduced to a 
Saturnicentric pofxtion, is about the 19th degree from the point Aries reckoned 
upon the ring. 


ff. (i). 


(N) 5 h. 24' 39". 43 , ,s. 

3 


(O) 8 h. o' 21". 53°, o. 


Nov, 


43 3 Dr. -Herschel’s Obfervations on the 

Nov. 13. 22 33. Oa the following fide (P). 

Nov. 15. 23 33. By a figure, nf. Saturn at a great dif- 
tance (Q). 

Nov, 19. 22 15. Dift. of the 5th. fat. ift meafure 8 54,94 

but too fmall. 

22 28. — — 2d — 8 58,28 

22 43* • •— 3^ — — 8 58,23 

22 54 * — — 4th — 8 58,85 

Mean of the three laft meafures 8' 58 ", 45 - 

This, when the exact inoJ ination of the orbit is afcertained, 
muft be brought to the greateft elongation, and alfo reduced to 
the mean diftance of the planet from the fun. 

Dec. 2. o 56. 1 he 5th fat. is in its calculated place (R). 

Dec. 5. o 10. As the calculation gives it (S). 

Dec. 16. 23 59. At a great diftance preceding (T). 


Obfervations on the fourth fatellite of Saturn . 

July 18. 19 50. The 4th fatellite is about 6 or 7 0 np. R. (A). 

July 23. 19 29. About 3I dia.of t? following the body ( B • 

a ' " cl , i 1 * ' " 0 

(I ) 651 44. 66,5. (Q) 6 43 53. 75,6. 

(R) 7 59 46 . 152,8. (S) 7 2 7, 166,2. 

(T) 6 7 58. 215,4. (A) 11 52 21. 284,0. 

(B) 11 11 47. 36,4. Following or preceding the body, denotes that we 

are to reckon from the nearefl: part of the circumference, and not from the 
center; but it is alfo to be obferved, that eftimations in diameters, when they 
exceed one, or one and an half, are not intended as meafures, but merely to 
point out the lituation in a very coarfe way $ fo that we are to look upon the calcu- 
lation as not difagreeing with this etfimation, though we fliould find the fatellite 
confiderably farther from the body. 

1 July 


4 39 


Satellites of the Planet Saturn. 

July 27. 20 2 7. 4 or 5 dia. following (C). 

July 28. 19 40. Near 4 dia. following (Ef). 

Aug. 18. 21 11. Many dia, preceding (E). 

Aug. 28. o 14. About 4! dia. of \ following the body (F). 

Aug. 29- 22 18. 3 dia. of \ following the body (G). 

Au g* 3 1 * 20 About 2J dia. of j? p. the body; a few fe- 

ccnds farther off than the 2d fatellite, and a little fouth of 
it (H). 

Sept. 8. 2230. About 2f dia. of ij following the body (1). 
Sept. 10. 19 42. Following Saturn (K). 

. 1K 20 2 ^* Following ij , too far to eftimate by the 
diameter (L). * 

Sept. 13. 22 17. By a figure, at a diftance following (M). 
Sept. 14. 20 33. About ij dia. of the ring following (N). 

0 42. 1 1 dia. of R. f. the edge. 

1 24. 1 dia. of R. f. the ring; exaftly in the line. 

oept. 16. 19 37. Not quite 1 dia. of the ring preceding (O). 

22 15. if dia. of R. p. the edge, and a little fouth. 

23 59. Near if dia. of R. preceding the edge of the ring. 

. Se Pf* *9 4 8 - About 3 dia. of the ring p. the projec- 
tion (P). r J 

Sept. 18. 21 15. Almoft at its greateft diftance p. (Q). 


( c ) 11 53 55 * 127,5. 

(E) is 11 27. 264,7. 

.(°) 11 35 5 ■ 154.2. 

(I) 11 7 48- 20,3. 

(L) 8 52 22. 86,1. 

(N) 8 47 34. 154,0, 

( p ) 7 5 ° 55 - 221,* 


h. / 

,(D) n 3 7. 149.3* 

( F ) J 3 34 42. 133,4. 
(H) 9 57 29. 198,0. 

( K ) 8 12 24. 62,8. 

(M) 10 35 13. i 33)0> 

(°) 7 43 52. 198,3. 

(Q-) 9 J 3 45 * 245,0. 


Sept. 


,.q Dr. Herschel’s Obfervations on the 

Sept. 20. 23 24. At a great diftance p, and a little n. (R). 
o 40. I can fee the 4th fatellite of Saturn without an eye- 
glafs in the 20-feet fpeculum by drawing back the eye about 
three or four feet. 

2 1 . Sept. 21 15. At a good diftance preceding, and a little 
north (Sj. 

Sept. 23. 22 33. The 4th fatellite emerged a few feconds 
a(TQ< it is now in the line of a tangent to that part of Saturn 
where the projeftion of the ring comes from the body (T). 

22 51. | of the projeftion (V) following the body of h; 
and about 2 of its own diameters north of the ring ; or not 
quite half way northwards between the center of h and the 

northern limb. 

Sept. 24. 19 56. About 2 of its own dia. nearer the ring 

than the 3d fat. and a little more north. 

20 48. The 4th advances to its conjunction with the 3d. 

22 47. The 4th is paft by the 3d. By a figure, it is lefs 
than one of its diameters paft the 3d fatellite, and is more 

north than the 3d (W). 

Sept. 19 34. It purfues its track (X). 

Oft. 1 2. 20 37. At a great diftance following (Y). 

Oft. x 5. 20 54. Many diameters of Saturn f. (Z). 

22 20. The 4th fat. at a confiderable dift. f. 




O 

292,.2 


(S) 


h. 

9 


/ // 
1 59. 


312,8. 


(R) 11 H 33* 

(T) 10 11 55. 359*2. 

[V) The diftance from the body of Saturn to the end of the projecting part o 
the ring, I call the projeftion, and have made ufe of it as a meafure for 

eilimating. 


(W) 10 21 57. 
00 7 1 39- 


O 

22,O b 

66 , 5 ^ 


h 

/ // O 

(X) 7 S 33* 41,6. 

(Z) 7 6 50. 134,4* 


Oft, 


Satellites of -the Planet Saturn. 441 

O fit. 16. 20 16. 2 i dia. of Tj following the body, 

21 59. The colour of the 4th Satellite is red, or inclining to 
red; it approaches towards a conjunction with the 3d. 

o 9. The 4th is very nearly in conjunction with the 3d ; it 
is about \ of its own dia. nearer to Saturn than the 3d, 
and near one dia. of the .3d fatellite more fouth than the 
3d (A). 

Oa. 18. 20 18. 2l dia. of vp. the body. 

21 51. About 2f dia. of i? preceding (B). 

Oa. 20. 20 50. At a. great diftance preceding (C). 

Oa. 28. 21 1. At a great diftance following (D). 

Oa. 29. 21 49. At a good diftance ff (E). 

Oa. 30. 20 53. At a great diftance following (F). 

Oa. 31. 21 13. At a confiderable diftance following (G). 

Nov. 2. 21 6. The 4th fat. is invifible. 

21 51. I cannot fee the 4th fatellite (H). , 

22 53. The 4th fat. is not vifible ; I looked for thefhadow 
of it upon t> , but could not perceive it. The weather a little 

hazy. 

23 21. Upon the dark equatorial belt of i? , on the f. fide, 
near the edge of the dilk, leems to be a final! black Ipot which 
is darker than the reft of the belt. 


(A) 

b. 

IO 

» if 

17 22. 

i6o,'i. 

(B) 

h. , 
7 5 i 

// 

54 ® 

! 

O 

203,0. 

(C) 

6 

43 l 3 * 

247.2. 

(D) 

6 22 

47 - 

67 . 9 - 

(E) 

7 

6 44. 

91,2. 

(F) 

6 6 

57 ® 

II2,S> 

(G) 

6 

22 59. 

1 3 S> 7 * 





(H) 

The tables I 

ufed at the time of this obfervation being different from my 

• a • i r 


quently vifible again* 

Vol. LXXX. 


23 29 


1 


M m m 


442 Dr. Her sc h el’s Obfervations on the 

23 29. A protuberance on the fp. part of 1? ; I fuppofe it to 
be the 4th fatellite emerging. 

23 31. The black fpot upon the equatorial belt feems to be 
a little advanced towards the preceding fide. 

23 38. With 300 the latellite is very nearly detached; the 
black fpot keeps advancing; it is a very little north of the 
equatorial belt, but part of it is upon the belt. 

23 43. The black fpot is a little more than 4 of the dia. of 
t? advanced from the f. fide towards the center. 

23 46. The fatellite feems to be detached. 

23 47. With 300, it is detached ; and the black fpot keeps 
advancing. 

23 57. The black fpot is advanced fo as to be | of its way 
towards the center ; the 4th fatellite is near \ its own dia. 
clear of the edge. 

o 13. The black fpot a little more than half way towards 
the center ; it is much darker than the belt. 

o 34. The black fpot is not arrived to the center yet. 

o 53. The black fpot is not come to the center, but does 
not want much of it. 

0 57. It is more upon the belt than it was before ; that is, 
more fouth. 

1 6. The black fpot is not yet come to the center. 

1 10. It is drawn towards the fouth, fo as to be nearly in 
the middle of the equatorial belt. 

1 11. It is not far from a central pofition. 

1 15. It is not come to the center yet. 

1 18. The black fpot is very near central. 

1 21. Very near central. 

1 25. Begins to be in the center. 

1 30. 


3 


443 


Satellites of the Planet Saturn . 
i 30. It Is in the center (I). 

Nov. 3. 22 1. The 4th fat. about 3 dia. p. the body (K). 
Nov. 4. 22 17. At a confiderable diftance preceding (L). 
Nov. 7. 22 9. At a good diftance preceding (M). 

Nov. 8. 20 46. At a good diftance p. (N). 

Nov. 10. 21 3. The 4thfatellite not yet vifible* 

21 32. Not yet vifible. 

22 26. Not yet vifible. 

23 24. About i dia. of J? nf. (O). 

Nov. 13. 22 33. On the following fide (P). 

Nov. 15. 22 33. Following ^ at a good diftance (Q). 

Nov. 26. o 28. The 4th fatellite is emerged fome time paft. 
o 30. It is nearly in conjun&ion with the 6th. By a figtire, 

it is half the diameter of the 6th nearer to Saturn than the 
fixth, and north of it (R). 

Nov. 30. 23 36. Dift. of the 4th fatellite 3' 12". 379. 

23 42. 2d meafure — 3 to .972. 

23 52. 3d — — - 3 10 .494. 

23 59. 4th — — 31° .579. 

Mean of the four meafures 3' ii''.io6 (S). 

Dec. 

(X) jo h. 31' 25", 5. 184°, 8. An extrad of thefe obfervations being printed 

in my la ft Paper, I am to remark, that here the time is uncorfeded ; but the 
corredion for this evening being— 8' 8", 7, it will be feen, that in the former 
Paper — 8' has been applied to all the times, and — S'' 9" to the time of the exad 
conjundion. 


6. / // 0 


in o 

(K) 6 59 4. 204, t. 

(L) 

7 ii 6. 226,9. 

(M) 6 51 21. 294,4. 

(N) 5 24 39. 315,6. 

(O) 7 54 22. 3,1. 

(P) 

6 51 44. 69,9. 

(Q-) 6 43 53- ”5> 0 * 

(R> 

7 57 23* 4,4- 


(S) The middle of the time to which we may fuppofe the meafures to anfwer 

M Hi m 2 Is 


444 Dr. Hekschel’s Obfervations on the 

Dec. 2. o 56. In its calculated place (T). 

Dec. 5. o 10. As the calculation gives it (V). 

Dec. 16. 23 59. At a great diftance following (W). 
o 43. The- 4th fatellite, with a power of about 500, fliews 
a pretty confiderable, vifible dilk (X). 


Obfervations on the third fatellite of Saturn . 

July 18. 19 50. The 3d fatellite about 1 or 2° ff. R. By a 
figure, at a confiderable diftance (xA). 

, July 23. 19 29. Near 2 dia. of v following (B). 

July 27. 20 27. About 2f dia. of h following (C). 

July 28. 19 40. The 3d fat. f dia. following \ ; it is much 
larger than the 2d, and a little more north. 

22 34. f part of a dia. following (D). 

Aug. 18. 21. 11. if dia. of i? following the ring (E). 

Aug. 28. 014. Full 2 dia. f. t? (F). 

is 23 h. 48', or 6 h. 59' 48" mean time. And by computation the apparent place 

of the fatellite at that time was 93 °,' 77 8 , which is 3 °> 77 8 or 3 ° 4 &' 4 1 A 5 2 P aft 
the greateft elongation ; therefore its diftance, if it had been meafured at the 
greateft elongation, would have been 3' 1 1" $22. This quantity brought to the 
mean diftance of Saturn from the fun, amounts to 3' 

/ // o • " ° 

(T) 7 59 46. 139,8. (V) 7 2 7. 206,6, 

(W) 6 7 5?- 93> 6 - 

(X) And from its ruddy colour (fee 06 t. 16.) we may furmife it to have a 
confiderable atmoTphere. This fatellite, therefore, feems to approach more to 
to the condition of., a planet .than any of the fourteen known fatellites.. 



h. t 

//» 

0 


/ JL 

0 

(A) 

II 52 

4 l * 

85.5* 

(B) 

II II 47. 

121,9. 

(C) 

” 53 

55* 

83,1. 

(D) 

5 3 S6 39- 

169,6. 

(E) 

11 11 

27. 

35 »°* 

(?) 

13 34 42- 

120,6. 


7 


Aug. 


Sat dikes of the Planet Saturn . 

■ . • ■ i 

Aug. 2:9. 22 21. A fatellite 011 the edge of the preceding 
arm (G). 

23 1 . The fat. a very little feparated from it. I fuppofe it 
to be the 3d, on account of its fize and brightnefs. 

23 41. The fatellite is now folly detached, fo as to be near 
| of the projection preceding the end of it. 

Aug. 31, 20 56. The preceding arm, about the middle, 
feemsto be charged with a fatellite; power 157 (H)< 

213. With 300, the fame as before. 

Sept. 8. 22 30. The 3d fat. about 2 f or 3 dia. of Saturn p. 


the body (I). 

Sept. 10. 19 42. The 3d following Saturn (K). 

Sept. 11. 20 26. 1 1 dia. of J? f. the body of t? » 

22 36. 1 dia. of t? f. the body. 

o 16. The 3d a little lefs than the projection from the £ 


edge. 

0 34. | of the projection following the ring. 

1 57; A little lefs than \ the projection f. the ring (L). 

Sept. 13. 22 2. The 3d, 1 J dia. of R„ preceding the edge 

of R. (M). 

Sept. 14. 20 27. The 3d fat. f the projection f.R. (N). 

21 55. if of the projection f. and a very little norths 
042. 2 projections following. 

1 24 Near two projections following. 

Sept. 16. 22 18. (O)i 


h. 


h. 


!» 


(G) 

II 

38 

5 - 

^ 93 ’ 9 **' 

(H) 

10 

5 27- 

34 ®> 3 ' 

(I) 

I I 

7 

48. 

269,9. 

(K) 

8 

12 24. 

59 . 7 - 

(O 

H 

22 


I 59 » 9 * 

(M) 

10 

20 15. 

306,1. 

(N) 

8 

41 

35 - 

20,4. 





(O) 

10 

24 

26. 

185,6. 

By this it appears that the 3c 

1 fatellite was invifibfe ; 


but obfervations being made on a fatellite, by miftake fuppofed to be the third, 
they wilhbe found among thofe of the 6th, to which they belong. 


Sept. 


446 Dr. Herschel’s Obfervations on the 

Sept. 17. 19 48. The 3d fat. i| dia. of the ring precedin t 
the projection (P). 

Sept. 18. 21 I5 V J of the projection, or if dia. of the fa 
tellite preceding the edge of the ring. 

21 45. 5 of the projection preceding R. 

2! 53. The 3d almoft touches the R. 

21 59. Quite clofe to the ring, and a little north. 

22. 7. Not quite fo near but that I can ftill fee a fmall 
divifion. 

22 20. With 157, I can no longer fee a divifion between the 
3d fatellite and the R. 

22 22. With 300, the fat. is completely joined to the R. 
but fo as to make it appear a little longer, and a very little 
knotty towards the north (Q). 

Sept. 20. 23 27. The 3d fat. i| projection f. R. It is within 
lefs than the diameter of the 2d fatellite preceding the 2d, and 
a little more fouth (R). 

23 51. The 3d fat. is now more feparated from the 2d. 

0 45. 1 ? projection f. R. 

1 22. 1 projection f. R. 

Sept. 21. 21 15. 2§ projections preceding the edge. 

22 44. Near 3 projections p. R. (S). 

Sept. 23. 22 51. The 3d fat. 1 projection f. the edge (T). 

Sept. 24. 19 56. ii dia. of R. f. the edge j about 2 diame- 
ters of the 4th fatellite farther from R. than the 4th, and a 
little more fouth. 

20 48. It advances towards a conjunction with the 4th. 

I It O '■ I U ° 

(P) 7 50 55. 256,9. (Q) 10 20 34. 345,0. 

(R) n 17 33. 147,6. (S) 10 30 44. 224,8. 

(T) IO 29 52. 24,3. 


22 47. 


Satellites of the Planet Saturn . 447 

22 47. It is paft by the 4th. By a figure, it Is about half 
its own diameter paft the conjunction, and is more fouth than 
the 4 th (V). 

Sept. 25. 19 34. (W). 

Oft. 12. 20 37. The 3d fat. about 3} dia. of f? f. the 
body (X). 

Oft. 15. 20 47. 1 1 dia. of i? p. the body. 

21 30. A little more than 1 dia. of t? from the body; and 
its whole diameter north of the line of the projection. 

22 25. The 3d fat. will be in conjunction with the 6th, in a 
very (hort time, the 3d being ftill a little preceding. 

22 39. The conjunction is fo complete now, that I have 
loft the 6th. The 3d, however, appears to be a little length- 
ened out towards the fouth. Diftance from the body barely 
one diameter of f? ; or juft one dia. of \ including the dia. of 
the 3d (Y). 

2 3 54* Near two of its own diameters paft the conjunction 
with the 6th. 

0 59. The ift, the 3d, and the 6th, are at equal diftances 
from each other. 

114. The 3d is nearer to the ift than to the 6th. 

1 35. The 3d approaches to a conjunction with the ift. 

I 45. The 3d is very near its conjunction with the ift. By 
a figure, it wants lefs than i a dia. of the 3d. 

Oft. 16. 20 16. The 3d, if dia. of i? following the body. 

21 59. It draws towards a conjunction with the 4th. The 
colour of the 3d is inclining to blue. 

(V) 10 h. 21' 57". io3°,6. 

(W) 7 h. 5' 33", 17a 0 , 5. Hence it appears that the fatellite could not be. 

feen this night. ' 

(X) 7 h. i' 39". 88°,2, (Y) Sh.51'33". 333^5 . 


_44S Dr. HersChel’s Obfervations on the 

o o. The 3d is in conjunction with the 4th, or 1 of t’n- 
. dia. of the 4th fatellite paft the coujundtion ; and one of its 
own dia. more north than the 4th ; that is, there is a vacancy 

between them of one dia. of the 3d (Z). 

Oft. 18. 20 18. 1 dia. of i ? preceding the body. 

’ 21 51. il dia. of b p. the body (A). 

Get. 20. 22 19. With 300, 1 fee the 3d fat. emerging; 

about i of its own dia. is out, at the following fide of b . 

32 44. At the diftance of | of its dia. following the body (B>. 
o 8. The f. projection paffes over the 3d fat. juft fo as to 


clear it. , 

Oft. 28. 21 1. The 3d about 3 dia. of b p. the body X). 

Oa'. 30. 20 53. About 3 dia. of b following the body (D). 

. oa. 3 1.’ 2 1 13. 4- ^a. of b following the body. 

21 <7. There is a complete conjunaion between the 3d fat. 

and the 2d; the following arm of the ring pafl’es exaaiy be- 

'tween them, and points to the 6th. The diBanee between the 

„d and 2d is about i the diameter of the 3d fatellite, the 2d 

being to the north, and the 3d to the fouth (E) 

,, 0 I can fee that the conjunction between the 3d and 2d 


fatellites is paft. . . , /t? . 

2 „ The 3d, i dia. of b following the body (F). 

4 49 . The 3 d approaching to a contaa with the body, but 
I can fee a divifion yet. 

23 5,8. A divifion ftill vifible between the 3d fatelhte and the 


body of b • 

lid { u © 

(Z) 10 17 22. 57 > 9 e 

(B) B 36 54. 1 

(D) 6 6 57. So, 4. 

(F) 8 22 39. 


h, 

(A) 7 
(C) 6 
(E) 7 


/ // 

5i 54- 

22 47. 
6 51. 


© 

209,4. 

281,8. 

163^5* 


) 


Now 


Satellites of the Planet Saturn . 


44p 


Nov. 2. 21 6. The 3d fatellite, i| dia. of i? p* the body; 
juft following the 2d, but a little more north (G). 

21 44. 1 1 dia. of t? preceding the body. 

Nov. 3. 22 1. 2j dia. of t? f. the body (H). 

Nov. 4. 22 17. About 2 dia. of t? following the body (1), 
Nov. 7. From 21 h. 28 7 to 23 h. 12 ' (K). 

Nov. 8. 20 46. At a confiderable diftance following (L). 
Nov. 9. 1 2. i. dia. of t? following the body ; its whole dia. 
is fouth of the arm (M). 

Nov. 10. 23 30. As the calculation gives it (N). 

Nov. 13. 22 33. On the following fide of i? (O). 

Nov. 15. 22 33. At fome diftance, preceding (P). 

Nov. 16. 22 50. (Q). 

Nov. 21. 1 54* The 3d, about i\ dia. of t? f. the body (R). 
Nov. 25. 1 21. (S). 

Nov. 30. 23 47. The 3d fat. about 2| of its own dia. fol- 
lowing the 6th (T). 

Dec. 2. 23 36. J of the proje&ion p. the body ; its whole 
diameter is to the fouth of the arm. 

022. The 3d, the 1 ft, and the 6th, nearly at equal diftatices 
from each other, 

^ • / // O f f, O i 

(G) 6 8 9. 319,6. (H) 6 59 4. 42,5. 

(!) 7 11 6. 122,5. 

(K) From 6 h. io' 28" to 7 h. 54' 11". 358°, 3 to 4°,0, and confequently 


invifible. 



*** it! O 

(M) 9 36 1. 169,1. 

(O) 6 51 44. 118,8. 

(Q.) 6 56 55. 358,2. invifible. 

(S) 8 52 10. 1,8. therefore invifible. 


(N) 8 o 21. 243,5. 

(P) 6 43 S3- 2 77.8. 
(R) 8 40 57. 42,4. 

(T) 6 58 48. 33,9. 

Vol. LXXX. 


o 50 


N n n 


/>. Herschel’s Obfervattons on the 
n 'g. The 3d and lft are in conjunction with a little fpace 
between them; the 3d being to the louth, and the ift to the 

north (V). 

Dec. 5, o 10. As the calculation gives it (W). 

Dec. 16. 23 59. 1 i dia. of b p. the body (X). 


0!)JervciUons on the fecond fatellite cf Satin n. 


July 18. 19 50. The 2d fatellite in the line of the ring p. 

Saturn ; but about 2 or 3 0 north (A). 

July 23. 19 29. | dia. of h preceding (B). 

July 27. 20 24. Upon the ff. part of the R. are two fmall 
bright points, the largeft is to the fouth, and is neared: to the 

body of 1? . (C). _ . 

20 29. The largeft of the knobs is about | dia. of ij from 

the body. Memorandum, I have no doubt, but that the large 

knob is the 2d fatellite ; I could nearly fee its whole diameter 

to the fouth of the ring, but not feparated. Clouds came 

on (D). 

July 28. 19 40. The 2d fat. of b i dia. following. 

22 34. Almoft a dia. f. (E). 


h . 


h. 

(W) 7 
(A) 11 52 21. 271,6. 


/ u 
2 7 - 


o 

72.4. 


(V) 7 S3 47- r9 6 >3- 

(X) 6 7 S 8 - 22 5>5- 
(B) 11 11 47- 2 °5» 8 * J . , . 

(CJ By calculation we find that thefe two bright points were the 2d and &th 
fatellites ; but at the time of thefe obfervations I only took down phenomena as 
they prefented themfelves, leaving a folution of them to future confiderations. 
See Note (B) to the 6th fatellite. 

(D) uh, 55' 55". i6° 5 o. (E) S*' 39 " I 5 ^°> 7 * 


Aug. 


Satellites of the Planet Saturn. 45'r 

Aug. 1 8. 21 ii. f dia, f. R. (F). 

Aug. 28. o 14. Near 2 dia. of ^ p* the body (G). 

Aug. 29. 22 18. About 1 dia. of t? p. the body (H). 

Aug. 31. 20 48. A few feconds nearear to i? than the 4th 
fatellite, and a little more north (I) 

Sept. 8. 22 30. The 2d fat. if dia. of t? p. the body (K). 
Sept. iOe 19 42. The 2d within 1 or 2 of its own diameters 
of the edge of the projection (L). 

23 2. In viiible. 

Sept. 11. 20 26. The 2d, if dia. of i? preceding the body. 
22 36. if, or almoft if dia. of % preceding the body. 

1 34. if of the projection preceding R. 

1 57* 1 proj e &io n P* R* (M) 

Sept. 13. 22 6. There are two fatellites emerging inftead of 
one (N). 

22 13. With 300, the neareft, if of its own diameters pre- 
ceding the projection. This I take to be the 2d fatellite (O). 
Sept. 14. 20 27. Barely 1 projection p. R. and a little north. 

21 55. The 2d f 1 dia. of the fatellite p. R. (P). 

22 23. The 2d, is now vanifhed (Q). With 300, I think 
there is about f dia. of the fatellite left. 

22 30. There now, certainly, is nothing left of the 2d fat. 
Sept. 16. 19 39. The 2d fat. if of the projection p. R. (R). 

h» / // O k* / U O 

(F) II II 27. 26,8. (G) 13 34 42. 276,0. 

(H) 11 35 5. 36,7. (I) 9 57 29. 291,0. 

(K) 11 7 48. 270,3. (L) 8 12 24. 157,5. 

(M) 14 22 27. 322,9. 

(N) See the obfervation of the I ft fat. Sept. 13. 

( O ) IO h. 31' 13." 205°,O. (P) 10 h. 9' 2 1 /r . 334°, 6.. 

(QJ The word vaniflied is here probably meant to denote its be^ng gone upon 
the ring, to the projection of which it was approaching 28' before. 


W 7 h - 45' 48"- 224 0 , 9. 


N n n 2 


22 15. 


4 ^ 2 Dr. Herschel’s Obfervations on the 

22 1 5. 1 dia, of from the edge of the R. preceding, 

and exadlly in the line of the R. 

23 59. Almoft 1 dia. of the R. preceding the edge of it. 

1 3. About ij dia. of \ from the preceding edge. 

Sept. 17. 19 48. (S). 

Sept. 18. 21 15. The 2d fat. i| of the projection f. the 
edge; it is 1 dia. of the iff Satellite nearer to \ than the ift, 
and a little more fouth. 

22 35. A little lefs than 1 projection f. the edge. 

23 14. About | of the projection f. the edge. 

012. | of the projection following, and a little fouth. 
o 27. With 300, the 2d fat. 1 of its own dia. f. the R. 

051. With 157, the 2d fat. clofe to the R. fo that no divi- 
fion can be perceived (T). 

o 55. With 300, the fatellite touches the R. and is a little 

fouth ; its whole dia. is ftill out. 

o 58. With 300, about | of the dia. of the 2d fat. may yet 

be feen. 

Sept. 20. 23 27. The 2d within one of its diameters fol- 
lowing the 3d, and a little north (V). 

23 31. The 2d is now more feparated from the 3d. 

0 45. 2 projections f. the edge of the ring. 

1 22. 2| projections f. R. 

Sept. 21. 21 20. (W). 

Sept. 23. 22 51. Almoft i dia. of the R. f. the edge (X). 

(S) 7 h. 50' 55'''. 356,8 invilible. (T) I2h. 49' 10" . I 55 °» 7 * 

(V) 1 1 h. 17 7 33". 50°,6. 

(W) 9 ; h.< 6' 58". 170^2 Gonfcquently invifible. 

(X) joh. &jf 52". 8i°,0o 

Sept, 


Satellites of the Planet Saturn . 453 

Sept. 24. 19 49. The 2d, upon the point of the ring p ; 
but I can fee no vacancy. 

19 56. With 300, the fame appearance nearly ; but the 
weather is too hazy, and the planet too low to bear it well. 

20 45. The 2d fat. begins now to project a little, and is a 
little fouth of the ring (Y). 

20 48. I can fee a divilion between the 2d fat. and the R. 

Sept. 25. 19 34 to 22 h. 38' (Z). 

OCt. 12. 20 37. The 2d fat. one full dia. of t? following the 
body (A). 

OCt. 15. 20 54. The 2d fat. if dia. of t? f* the body (B) e 

23 20. About if dia. of i? following. v 

OCt. 16. 20 16. The 2d fat. | dia. of \ , or a little lefs p« 
the body (C). 

20 36. | dia. of 1 ? p. the body. 

22 35. 1 J dia. of 1? p. the body. 

on. if dia. of t? p. the body. 

©&. 17. 21 30. The 2d fat. 1 projection p* the body of h ; 
very hazy weather (D). 

(Y) 8 h. 20' 1 7". 200°, 7. 

(Z) From 7 b. 33" to 10 h. 9' 3", the fatellite is not mentioned in my 
observations ; though by calculation it appears, that its Situation was from 325°,6 
to 342°, 3 5 and that therefore it ought to have been feen. I conclude from this 
that fome particular caufe mull have rendered it invifible. Moft probably it 
Suffered an occultation from the iff fatellite, which was fituated in fuch a manner 
as nearly to cover it the whole evening ; in this cafe, the observation of the iff 
belongs alfo to the 2d, Since their diameters would certainly run together fo as, 
perhaps, if the occultation was not always central, to form only one fatellite, of 
rather a larger diameter than either of them. 

k* I U O / // O 

( k ) 7 1 39- 42,4. (B) 7 6 5°- 77,7- 

(C) 6 25 1. 205,4. (D) 7 34 53. 343,4. 

0£V. 


. t 1 Dr. Herschel’s Obfervatiom on the 

43 T ' 

Oft. iB. 20 1 8. The 2d fat. near 2 dia. of fj f. the body. 

21 51. ij dia. of r? f. the body. 

0 52. It approaches to a conjunftion with the ift. 

1 25. The 2d fat. very nearly in conjunftion with the ift. 

x 28. The conjunftion is complete (E). By a figure, the 2d ia 
towards the north of the ift; but they leemto be in contaft. 

Oft. 20. 21 17. The 2d fat. is emerged fome time ago, and 
is now 1 \ of its own diameters from the body of i? . I per- 
ceived the fatellite as a protuberance before 20 h. 50 (F). 

Oft. 28. 20 58. The preceding arm, on the north fide, very 
near to the body, contains a confiderable fatellite. 

21 5. The 2d fat. is clofe to the body, on the p. fide, to the 

north of the ring (G). 

Oft. 29. 21 49. The 2d about 14- dia. of i? f. the body (H), 
Oft. 30. 20 53. About 2 dia. of i? p. the body ( 1 ). 

Oft. 31. 21 13. The 2d, | dia. of i? following the body. 

21 57. There is a complete conjunftion between the 2d and 
3d. The arm pafles exaftly between them, and points to the 6th. 
The diflance between the 2d and 3d is about f the dia. of the 3d ; 


the 2d fatellite being to the north, and the 3d to the fouth (K). 

22 o. I can fee that the conjunftion between the 2d and 3d 

fatellites is paft. 

23 13. The 2d fat. is paft the conjunftion with the 6th. 

Nov. 2. 21 6. The 2d fat. juft preceding the 3d, but a little 

l 

more fouth. 

2144. 2 dia. of p. the body, and'H little more fouth than 

the 3d fatellite (Lj. 

( ' | 

^ ^ ® j £ Q 

(E) 11 38 17. 137,2. (F) 7 10 I 5 » 9 * 

( G ) 6 26 46. 344,6. (H) 7 6 44. 119,8. 

(I) 6 6 57. 245,9, (K) 7 6 51. 22,9. 

■(L) 6 46 3. 284,1. vr. 


f 


Satellites of the Planet Saturn . 4 c 5 

Nov. 3 .22 I . The 2d fat, 2 dia. of \ following the body (M). 

Nov. 4. 23 42/ The 2d fat. f dia. of P the body (N). 

23 57. The dia. of the 2d fatellite is intirely fouth of the 
p. arm. 

Nov. 7. *21 28. The 2d and ift fatellites, about 1 dia. of ^ , 
or a little farther, p, R. 

21 53. The 2d fat. 14 dia. of i? p. the body (O). 

Nov. 8. 20 46 to 23 h. 40' (p> 

Nov. 10. 23 30. As the calculation gives it (Q). 

Nov. 13. 22 33. On the preceding fide (R). 

Nov. 15. 22 33. The 2d fat. is upon the preceding arm of 
the ring about half-way ; all its dia. is towards the fouth (S). 

22 49. The 2d is not quite to the end of the R. yet, but 
keeps advancing. 

22 56. f of the projection preceding the body, or \ want- 
ing to being at the end of the ring. 

Nov. 26. 22 27. The 2d is upon the p. arm ; its whole dia. 
is towards the fouth (T). 

o 28. The 2d is emerged feme time pail (V). 1 , 

Dec. 2. 22 50. The 2d fat. about 1 J dia. of \ preceding the 

body (W). 

Dec. 010. As the calculation gives it (X). 

h. , h. / N 

(M) 6 59 4. 56,9. (N) 8 35 52. 197,3. 

(O) 6 35 24. 220,9. 

(P) 3 24 39. 346,1. The firft part of the evening was not very clear, 

and afterwards, by the calculation, the fatellite was invifibie. 

h* /. ✓/ ,0 „ o 

(Q) 8 o 21. 263,4. (R) 6 31 44. 291,8. 

(S) 6 43 53. 194,2. (T) 3 34 43 - I 9 ^» 5 - 

(V) To emerge was here probably put for coming off the arm. 

(W) 5 h. 34' 6". 263°, 5. (X) 7 h. 2' 7", 306°, 3* 


Dec. 


45 6 

Dec. 16. 
body (Y). 


Dr. Herschel’s Obfervations on the 
23 59. The ad, about i| or 1*. dia. of ^ p. the 


Obfervations on the firjt fatellite of Saturn. 


July 18. 19 50. The following part of the ring of Saturn, 
which is a very thin lucid line, ends in a bright point like a 
very faint fatellite (A). 

I fuppofe the bright point on the f. part of the ring to be a 
very lmall fixed ftar (B). 

20 14. The bright point on the following part of R. feems 
to have its whole dia. towards the north ; and in all appearance 

adheres to the line. 

o 48. Poffibly the bright point on the nf. part of the ring 
may be one of the fatellites, and one of the before fuppofed fa- 
tellites may be a fmall fixed ftar (C). 


(Y)6h. 7' 58". 3 ° 7 °> 8 - . . 

(A) 11 h 52' 21". 146,7. This lliews, that the bright point was the lit 

fatellite. , . . 

(B) Being the firlt night of my viewing the fatellites this year, their place. 

were unknown. The 6th, which was in view, I took for the ill fatellite but, 
the 2d, 3d, and 4th being alfo before me, there remained only the fuppofition ot 

fome fmall fixed liar to account for the bright point. _ 

(C) The motion of the bright point on the ring led me to the fuppofition 0 
its being a fatellite ; and, to make room for one, it occurred, that one of the 
others might be a liar : for ftill the thought of an unknown fatellite did not 
happen to ilrike me. I Ihould have made an attempt to calculate the places of 
the fatellites by the manufcript tables of M. oe u Lande, which are now 
printed in the Connofance des Temps for 1791 ; but as there chanced to be 

an erratum of one day’s motion in the epoch* of all the fatellites for 1788, 0 

which I was not aware, I had fo little fatisfaflion from them the year before, t at 
1 laid them by as ufelefs, and refolved to inveftigate the epoch* and revolutions 
:0f the fatellites from my own obfervations. 


21 15 * 


Satellites of the Planet Saturn. 

2 1 15. The nf. bright point is advanced towards the body, 
fo that it no longer hangs at the far end of the ring (D). 

July 23. 19 29. (E). 

July 27. 20 27. One dia. of f. is a fmall fatellite (F). 

July 28. 19 40. The ift fat. if dia. of i? preceding the 
body (G). 

22 34. The 1 ft fat. as before. 

Aug. 18. 21 11. i| dia. of t? p. R. (H). 

Aug. 28. 09. 1 J or if projeftion f. R. or 1 dia. of t? from 
the body (I). 

Aug. 29. 22 18. About if dia. of t? p. the body (K). 

Aug. 31. 20 54. i f dia. of J? p. the body (L). 

Sept. 8. 22 51. (M). 

Sept. 10. 22 49 and 23 h. f (N). 

Sept. 


(D) 13 b. I7 ; 7". 158°, O. Hence we fee, that the fatellite had advanced 

II degrees in its orbit towards h , fince uh. 52' 2 which agrees with th© 
motion of the bright point. 

h - , /, 

(E) 11 11 47. 15,1. Therefore the 1 ft fatellite was not vilible. 

(F) II 53 55 * 63,5. It was the firft. 

(G) 11 3 7 . 247,5. The names of the Satellites were by this time 

afeertained, and I found that the above-mentioned manufeript tables agreed pretty 
well with my obfervations this evening. 

^* / // o f * 8 / // o 

(H) 11 11 27. 294,3. (I) 13 49 42. 60,4. 

( K ) 11 35 3 * 236,0. (L) 10 3 29. 245,4. 

(M) II 28 45. 342,9. Confequently the fatellite was invilible, or at leaft 

might eafily be overlooked, fo near the body upon the p. arm as it muft have 
been fituated ; but there was an obfervation made upon what is called the ill 
fatellite, which will be reported hereafter. See obfervations on the 7th fatellite, 
Sept. 8. 

(N) From 11 h. i 3 ' 54" to 11 h. 33' 51". 3°,i to 5°,l. The ift fatellite 

was invilible ; but two obfervations were made upon what is called the firft, which 
will be feen in the obfervations upon the 6th fatellite. Such miltakes may eafily be 

Vol. LXXX. O o o made 


45 8 


Sept. ii. i o 


Dr. Herschel’s Obfervations on the 
o. The i ft fat. about 2 of its own dia. p. the 


projection ; emerged fince I looked laft (O). 

1 34. Half a projection p. R. 
x re. | of the projection p. R. 

Sept. 13. 22 o. There is a fatellite emerging from the pre- 
ceding arm ; I take it to be the ift (P). 

22 6. There are two fatellites emerging inftead of one. 


very little fouth. 

23 22. With 300, 1 or 1 1 of its own dia. farther from (be 
R. than the 6th, and a little more fouth (QJ. 

0 42. ii projection f. R. 

1 24. 1 1 projection f. R. 

x 46. Much the fame as before. 

Sept. 16. 19 39. The ift fat. \ projection f. R (R). 

22 18. 1 1 projection f. the edge, and a very little fouth. 

23 59. About 1 dia. of b t. the edge of the R. 
i 3. | dia. of i? f. R. 

Sept. 17. 19 48. The ift almoft 1 projection p. R. (S). 
2038. 1 f projection p. R. 

Sept. 18. 21 15. The ift fat. if projeaion f. R. or one of 
its own dia. following the 2d fatellite (T). 

22 35. 2 projections following the R. 

made during the time of obfervation, as a few hours will bring one of the inner 
fatellites in view ; but with fuch accuracy of calculating the precife moment an 
fituation of the fatellites, as has now been ufed, there can be no doubt to which 


Sept. 14. 2 1 55- The ift fat 


22 13. 


2. The one that emerged firft 


irft, j of the projection p. R. 
j of the projection t. R. ana a 



(O) 13 25 37 - 21 °> 7 - 

(Q.) 1 1 36 6- 48 >.5* 

(S) 7 50 55 - 231.0. 


/ // o 

(P) 10 18 15. 207,4. 

(R> 7 45 5 2, 39-6. 

(T) 9 13 45. "2,8.' 


o 1 4 c 


459 


Satellites of the Planet Saturn* 

014. 1 1 projection f. R. 

Sept. 20. From 23 h. 24' to 1 h. 28 / (V). Notwithftanding 
my utmoft endeavour, I could not perceive the xft fatellite. From 
the tables I furmife that it might be under an occultation, or 
eclipfed by the 3d fatellite ; I looked for it above two hours. 
It could be neither in the (hadow of Saturn, nor in that of the 
ring. 

Sept. 21. 21 15. The ift fat. 2 projections p. R. (W). 

22 44. if or 1 J projection p. R. 

Sept. 23. 22 51. J projection p. R. and a very little north. 
It follows the 6th fatellite 1 dia. of the 6th (X). 

23 55. The 1 ft fat. almoft touches the ring; it may want 
one of its diameters. Clouds interrupted the obfervation. 

Sept. 24. 19 49. The firft fat. if projection ft R. or about 
one of its own dia. ft the 6th. 

20 45. The 1 ft fat. 1 full projection ft R. 

22 47. Clofe to the following projection (Y). 

Sept. 25. 19 34. The ift fat. 1 full projection p e the edge of 
R. and a little north. 

20 41. A little more than J projection p. R. 

22 38. The ift fat. has half its dia. projecting towards the 
north from the ring, on the preceding fide ; its place on the 
ring is about f of the projection from the body of ^ . The 
night is extremely clear (Z). 

o a. 12. 20 37. About | dia. of 1? p. the body. 

21 24. f projection of R. preceding the edge, and confidera- 
bly more north. 

(V) From nh. 14' 33" to 13b. 18' 13". no°,4 to 126°, 6. 

/TTT\ / n o ^ * / // o 

(W) 9 I 59. 283,5. ( x ) 10 29 52. 316,7. 

(Y) 10 21 57. 146,4. (Z) 10 9 3. 335,5. 

O 0 O 2 


22 6 . 


4 go Dr. Herschel’s Obfervathm on the 

22 6. The ift almoft touches the p. projeaion. 

22 24. It very nearly touches the p. projection . 
r 26. i of the projection p. the body of t? ; or, as it were* 
fattened upon the projection, $ from the end of it ( A). 

1 8. I fee nothing of the ift tat. 

OCt. 15. o 52. The ift fat. § projection from the body (B). 

0 59. The diftance of the ift from the body is almoft, but 
not quite, equal to the diftance of the ift, 3d, and 6th from 

each other, 

1 14. The firft is nearer to the 3d than the 3d to the 6th. 

1 35. The ift and 3d approach to a ccnjunCtion. 

1 45. The ift and 3d very near their conjunction. 

Oa. 16. o 11. The ift fatellite \ dia. of \ f. the body (C). 

1 20. ? of the projeaion f. the edge of the R. ; the weather 
remarkably clear. I can fee the R. very diftmaiy, fo as to 

judge with fafety of the projeaion. 

Oa. 18. 21 7. The ift fat. is lately emerged from the body 


of i? on the f. fide. 

2112. The emerged fat. 1 of its own dia. f. the body of i? . 
21 32. Above 2 of its own dia. following ^ . 

2 1 31. The ift fat. 4 dia. of i? f. the body. 

22 36. Very nearly clear of thef. projeaion (D). By hiding 
the planet behind the field-bar very carefully, I can fee the 
projeaion of the R. very well on the f. fide. The preceding 
projeaion cannot be diftinguilhed fo well on account of the 

fatellites (E) that are upon it. 

0 52. The ift fat. approaches to a conjunaion with the 2d. 

1 25. The ift and 2d fat. very nearly in conjunaion. 


h ® q 

(A) 9 50 l'l. 336,0. 
(C) 10 19 22. 22,8. 

(E.) The 6th and 7th. 


**• / U O 

(B) ii 4 11. 198,0. 

(D) 8 |6 47* 3°> 8> 

I 38 


Satellites of the Planet Saturn . 461 

1 38. The conjunction is complete. 

OCft 20. 20 5. The ift fat. 4 dia. of j ? f. the body (F). 

20 50. It draws towards a conjunction with the 6th fat 
diftance 1 dia. of the ift. The 1 ft is a little towards the 
north. 

21 26. I can juft fee a very fmall divifion between the ift and 
the 6th. 

21 51. There is a perfeCt conjunction between the ift and 6th, 

OCt. 28. 21 1. The ift fat. 1 dia. of ^ ft the body. 

21 50. It draws towards a conjunction with the 6th, diftance 
1 full dia. of the ift (G). 

OCt. 29. 21 49. The ift about 4 dia. of ^ p. the body (H). 

OCt. 30. 20 53. The ift fat. J dia. of ^ f. the body (1)„ 

OCt. 31. 21 13. I dia. of t 2 P- the body (K). 

23 13. i- dia. of t? p. the body; its whole dia. fee ms to be 
north of the arm. 

Nov. 2. 23 26. I fuppofe the ift fat. to be upon the ft arm. 

o 8. The f. arm contains a lucid point at the diftance of 
4. dia. of ^ ft the body. 

o 34. The 1 ft fat. almoft | dia. of t? £ the body (L)» 

Nov. 3. 22 3. The preceding arm is loaded in two places ; 
at the far end, and about the middle. 

23 48. The ift fat. \ dia. of i? p. the body (M) ; there feeing 
to be another clofely following it (N). 


(F) 5 58 20. 31,3. 

{H) 7 6 44. 317,1. 

(K) 6 22 59. 332,7. 

(M) 8 45 47. 203,8. 

(N) It was the 6 th. 


/ >/ 0 
(G) 7 11 39. 127,0. 

(I) 6 6 57. 139,8, 

(U 9 35 35* J 9>7 r 


O 10. 


Dr. Herschel s Obfervations ok the 

O IO I can diftinguilh the two fatellites that follow one 

another upon the arm ; the diftance between them is 1 dia. of 

the fmalleft of them. _ 

Nov. 4. 22 14. The 1 ft fat. I dia. of * f. the body (O). 

22 57. The dia. of the ift fat. is north of the arm. 

Nov. 7. 21 28. The ift and 2d about 1 dia. of 1? , or a little 

more, p. the body (P). 

21 53. The ift fatellite i£ dia. of i? p. the body. 

Nov. 8. 20 46. \ dia. of i? f. the body (Q). 

Nov. 10. 23 30. The ift as the calculation gives it (R). 
Nov. 13. 22 33. On the preceding iide (S). 

Nov. 1 5. 22 33. About \ dia. of 1? p. the body (T). 

Nov. 16. 22 50. Upon the end of the f. arm (V). 

Nov. 21. o 54. ? dia. of i? f. the body (W). 

Dec. 2. 22 49. The ift fat. about 1 of its own dia. p. the 6th. 
2 3 38" ft i s ^ ie cotijunftion with the 6th, which it 

now follows, and it is a little more north than the 6th. 

o 22. The ift is equally diftant from the following 6th,, 

and the preceding 3d (X). _ 

o 50. The ift and 3d are in conjunction, with a little ipace 

between them, the ift being to the north. 

Dec. 5. o 8. (Y). 

(O) 7 h. 8' 6". 2i°,S. . . 

( P j 6 h . io' 28". 226°, o. By the equal diftance which is mentioned, it 

appears, that the ift and 2Q fatellites were in conjunflion ; and this agrees alfo 
with the next oblervation, compared with that of the 2d fat. Nov. 7th. 
h 

(Q) 5 4 39 - S°> 8 - 

(S) 6 51 44. 295,9. 

(V) 6 56 55. 148,6. 

(X) 7 25 51. 323,5. 


11 • / // o 

(R) 8 o 21. 92,7. 

(T) 6 43 53. 316,2. 

(W) 8 40 57. 35,9. 

(Y) 707. 172,1 invifible. 

Dec, 


Satellites of the Planet Saturn . 463 

Dec. 16. 23 59. The ift fat. a little more than 1 dia. of 

t? f. the body (Z). 

Dec. 24. o 5. (A). 

Dec. 25. 1 36. The ift fat. is upon the end of the f. arm (B). 

Obfervations on the fxth fatellite of Saturn . 

July 18. 19 50. The f if fatellite of t? exaftly in a line of the 
R. preceding (A). 

July 27. 20 24. Upon the ff part of the ring are two fmall 
bright points ; the largeft, to the fouth, is neareft to the body 
(B). and the fmalleft, to the north, is at the farther end (C). 

Aug. 28. 23 26. With the 40-feet reftedtor, I fee the five 
known fatellites of Saturn, and alfo another exa&ly in a line 
with the ring, interpofed between the 2d fatellite and the ring 
oil the preceding fide, while the ift, 3d, 4th, and 5th are on 
the following one. It has fo much the appearance of the other 
iatellites, and ranges fo well with them, that I have not a 
moment’s doubt but that it is a fixth fatellite. It is lefs bright 

k* t ,, o h. t n o 

(Z) b 7 58. 102,4. (A) 5 42 33. 184,3 i nv i^ l 8Ie. 

(B) 7 9 23. 26,3. 

(A) By computation for 1 1 h. 52' 2l x/ we find, that the 6th fat. was 302,4 >* 
which is exadly in the place where a fatellite called the firh was obferved ; but it 
appears alfo from the calculation which has been given in the note A of the ift 
fatellite, that this obfervation cannot belong to the real ift 5 the 6th fatellite 
therefore was feen this evening without being known ; and this explains all the 
difficulties which occurred with regard to the real ift fatellite. See obfervations 
on the ift fatellite, July 18. 

(B) It was the 2d fatellite. jSee obfervation on the 2d fatellite, July 27. 

(C) 11 h. 50' 56". I47°,i, which agrees exactly with the place of the 6th 

fatellite,, 

i than 


Dr. Herschel’s Obfervations on the 

than the reft, but feems to have light enough to be feen by my 

20-feet telefcope. # . rx . 

O 9. 20-feet reflector. The new fatelhte * of the projedion 

of the ring preceding the edge of the B. (D). 

o 20. A very fmall ftar about 6o° if. % , and 1 , dia. of 

u diftant from the body (E). 

j l6 . The fmall ftar is gradually left behind io as now to 
make an angle of about 35’ ff. b i « tl “ farae “ me tlre 

planet has earned along with him the new latell.te 

i 24. The 6th fatellite § of the projedion of the R. p. 

ring. y o re 

1 46. The fame fmall ftar is now only about 25 ft. b • 

1 49. The new fatellite is now not much more than \ the 

projedion from the ring. r A . 

2 2. Saturn is gone on, in a retrograde order with refped to 

the fmall ftar, and has carried along with him the new 1 co- 

vered fatellite. . rL . r 

Sept. 8. 22 30. The new or 6th fat. 4 of the projection of 

the R. direCtly preceding (F). 

Sept. 10. 22 49- The firjl fatellite lefs than the projection 

from the following arm ; extremely faint (G). 

24 4. The firjl fatellite the length of the projection following 

the arm ; it is fo faint that I cannot exped to fee the new 
fatellite (H). Sept. 


m) nb. 29' 4 2// * 2 94 % 2 « 

(E) This ftar was immediately taken notice of, to venfy the chfeovery of th. 
6th fatellite. 

( 45 ) \ I ih. 7 18' 54" J 9 86°, 8 . Which agrees perfedly with the 6th fatelhte, 

though it is here by miftake called the ift. , ;t 

<H) As I miftook the 6th fatellite for the ift, it was natural enough to - 


Satellites of the Planet Saturtj. 46 5 

Sept. 14. 21 59. I think I perceive a fatellite between the 
1 ft and the following projection clofe to the ring. 300 leaves 
it doubtful (I). 

2.2 23. The 6th fat. | of the projection f. R. ; fo clofe to 
the 1 ft that it requires great attention to be d:fhnguhhed. With 
300, the 6th is 1 or if dia. of the ift fat. nearer the R. than 
the 1 ft, and a little more north than the ift, that is to fay, very 

exactly in the line of the ring. 

23 45. With 460, the 6th fat. is very near one whole pro- 
jection f. R. 

0 42. The 6th fat. 1 full projection f. R. (K)» 

1 24. The new fat. 1 projection f. R* 

1 46. Very nearly, but not quite, 1 projection f. R° 

Sept. 16. 22 18. The third fatellite i the projeftion from 
the preceding edge of R. 

22 25. The third fatellite is extremely fmall, and hardly to 
be feen j but I have no doubt. 

23 59. The third fatellite a little more than f the projection 
preceding the edge. 

0 16. The third much lefs than the ift and 2d* partly owing 
to its proximity to the planet 5 but probably there may be an 
•apparent change of magnitude from a revolution upon its axis* 

1 2. The third about % of the projection p. R» (L)*' 

3 • Sept. 

Very faint, and of courfe to fuppofe that the night was not clear enough to fee 
the 6th, while at the fame time I was malting an obfervation on that very fatellite. 
But it muft here be remembered, that the time of Us revolution was not yet well 

( 1 ) The calculation for lOh. 13' 20" gives &\o, which fcews that the fatel- 


lite was there; 

(K) 12 h. 55' 53". 7 s°, 7 - 

(L) The 6th fat. was this evening 
Vcu.. LXXX. 


miftaken for the 3d j but the calculation for 

P P P *3 h - 


Dr. Herschei.’s Obfcrvations on the 
Sept. 17. 19 52. The 6th fat. 1 projection, or rather more 
£ the projection ; extremely faint. 

20 38. 1 full projection following (M). 

22 55 . j projection f. and a little fouth ; extremely fmalb 

23 49* j projection f. ano a iittie routh* 

0 58. | projection following. 

1 46, Near % of the projection following (N). 

Sept. 21. 21 10. The 6th fat. 1 full projection f. R* ; much- 

fainter than the ift ; hazy weather. 

21 20. 1 full projection f. the edge, and exaCtly in the liner 
of the ring. I fee it very well ; it is iefs than the ift. 

22 9. 1 1 of the projection f. the edge (O). 

22 39. Nearly 1 J projection f. the edge of the R. exaCtly in 

the line of the R., 

Sept. 23. 22 51. The 6th fat. 1 projection p. the edge; or 

1 of its own diameters p. the ift (P). 

Sept. 24. I 9 46. I fufpeCt the new or 6th fatellite to be I 

projection f. the edge (Q), 

19 49.. The 6th is very near I projection f. the edge ; it pre- 
cedes the ift fat. about 1 dia. of the ift. 

20 45. The 6th. a little more than. § projection, f- the* 

edge. 


33 h. 8' 59", which gives 243*, 7, fhews that thefe observations belong to the 6th ; 
and therefore explains all the difficulty about the fuppofed change of magnitude of. 
the 3d. 

(M) 8h. 40' 47". 97° 3 6* 

(N) The effiimation | is probably a miftake in writing down, and fhould. haver 
been J ; perhaps alfo fome change in the atmofphere, or other circumftance, may. 
have induced an error of eftimation, which, in fuch minute objects, will now. 


and then take place. 

(O) 9 h. 55 ' 53 "- 

(Q) 7 b. %\' 28". 


(P) IQ h. 29' 52". 254 0 , 3- 

Sept*. 


< 


Satellites of the Planet Saturn. 4 ^/ 

Sept, 25. 22 36. The 6th almoft * projeftion f. the edge of 
the R. 

23 42. The 6th fat. very nearly 1 projeaion f. R, (R). 

23 52. The 6th fat. is much larger than the ;th. 

Oa. 1 2. From 22 h. 6' to 1 h. 8' (S). 

0 58. The feventhfat. extremely fmall upon the point of the 
preceding projeaion, and a little towards the fouth. 

1 20. The diftance of the feventh increafes. The fatellite 
feems to be clear of the projeaion ; but I can fee no divifion 
yet, its whole dia. feems to be to the fouth ^ I fee it full aft, 
well as I faw the 6th, or rather better (T), 

1 35. The feventh is clear of the projeaion. 

Oa. 1 5. 20 47. The 6th fat, 1 dia. of ^ p. the body. 

21 34. The 6th about | of the projeaion p. the edge of R. 
or very near 1 dia. of i? p. the body ; juft ft. the 3d , it is in the 
line of theR. (V). 

22 25. The 6th fat. will be in conjunction with the 3d in a 

very fhort time, the 3d being ftill a little p. 

22 39. The conjunaion is fo complete now, that I have loft 
the 6th. The 3d, however, appears to be a little lengthened 
out towards the fouth. Diftance of the conjoined fatellites 

(R) 1 1 h. 12' 52". 67°, 7. 

(S) There were five obfervations made upon the 6th fatellite, but they belong 
to the 7th. There were alfo three obfervations made upon the 7th which belong 
to the 6th, and are here given ; we are to obferve, that the revolution of the 7th 
was not yet afcertained, and that, confequently, a miftake of one new fatellite 
for another could eafily be made. 

(T) nh. 43^53^. 220°, 9. The calculation of its place {hews plainly 

that it was the 6th; and the remark in this obfervation of its being brighter than 
the other fatellite perfe&ly agrees with the calculation. 

(V) 7 h. 46' 43". 246°, O. 


P p p 2 


barely 


4.68 Dr. Her sch el’s Observations on the 

barely i dia. of t? from the body; or juft i dia. of , in- 
cluding the dia. of the 3d fat. 

23 59. The 6th near 2 diameters of the 3d fatellite paft 
the conjunction. 

0 59. The 6th, the 3d, and the firft fatellites are at equal 
diftances from each other. 

1 3. The 6th is one dia. of 1? from the body. 

I 39. The 6th nearly 1 dia. of p. the body. 

061 . 16. 20 16. The 6th fat. f dia. of f. the body; too 
low to be very accurate. 

20 36. The 6th one full projedtion f. the body ; extremely 
faint. 

20 50. The 6th one projection ft the body. 

21 11. The 6th % of a projection ft the body. 

21 55. The 6th i projedtion ft trie ody, cr a little lefs (W)., 

22 5. The 6th advances towards a contact with the ft part 
of the body ; I can, however, ftili look between them. 

22 18. 1 can ftili fee between the planet and the 6th fat. 

22 22. The 6th lefs than its own dia, from the planet. 

22 25, It is in contadt with the body of h . 

22 41. I can ftili perceive the 6th fat. 

22 44, The 6th is not quite vanished. 

22 47. The fatellite is no longer vifible. 

Qdt. 17. 2i 30. The 6th fat. § projection f. the body, very 
hazy weather (X). 

Qdt. 18. 20 40. The 6th fat. is emerging from behind the 

3d. 

20 46. The 6th fat. which emerged from behind the 3d is a 
little north of the line of the ring, and of the 3d. 

21 36. 


(W) 8 h. 3' 44" i5i°,9. 

5 


(X) 7 h. 34' 53"; 49°,4. 


Satellites of ibe Planet Saturn . 


469 


zt 36. The 6th is going towards t? , and is about J dia. of 


22 51. | dia. of Tp p. the body. 

22 26. The 6th about 4 d i a r of i? p. the body. 

22 40. The 6th § dia. of t? p. the body. 

23 17. The 6th approaches to a conjunction with the 7th. 

23 37. The conjunction of the 6th arid 7th fatellites is 

pad. The fatellites are, however, too near the planet to fee 
exaCtly how they are placed. 

o 12. The 6th a little more than 1 of its own dia* p. the- 
body of Tp (Y). 

OCt. 20. 20 5. The 6th fat. 1} dia. of t? f. the body (Z). 

20 50. The 6th and 1 ft fatellites are drawing towards a con-* 
junction ;; diftance between them 1 dia. of the ift fat. 

21 26. I can juft fee a very fmall divifion between the 6th 
and the ift. 

21 51. There is a perfeCt conjunction between the 6th and 
the ift. 

22 22. The 6th fat. appears again. 

2243. The 6th is in the middle, between the ift and 2d 
fatellites. 

23 50. I perceive the 6th fat. near the 3d towards the 2d; 
and on the fouth of the line that joins the 3d and 2d; but 
nearer the 3d than the 2d. 

OCt. 28. 20 58, The 6th fat. about t projection f. the edge 
of the R. 

21 5. The 6th about J dia. of ^ f* the body (A). 

OCt. 29. 21 49. The 6th juft f. the ift (B). 


(A) 6 26 46. 47,5. 

(B) 7 644, 317,5* For the place of the ift, fee the lit fat. 0 £h 29* 


T) preceding the body. 


(Y) 10 12 31. 341,0- 



OCt, 


4 yo Dr. HerschEl’s Obfervations on the 

Oft. 30. 20 55. I fufped the 6th on the edge of the p. arm ; 

but moon-light is too ftrong. 

23 44. The 6th fat. | projection p. the edge of the R. 

23 55. The 6th fat. 4 dia. of h p. the body, 
o 42. The 6th fat. 14 dia. of t ? p. the body (C). 
oa. 31. 21 13. The 6th fat. 4 dia. of t? p. the body. 

2 1 57. The f. arm of the R. pafles between the 3d and 2d 

fatellites, and points to the fixth. 

„ ry. The 6th full § dia. of i? following the body (D). 

Nov. 2. 21 44. The 6th fat. 14- dia. of i ? p. the body, and a 

little north ; extremely faint (E). 

22 17. The 6th fat. 1 full dia. or 1 dia. of J? p- and a 

very little north. 

22 53. The 6th feems to be flill i T ' T dia. of h , or rather 
more, p. the body, but the weather is hazy and foggy. 

2 „ The 6th fat. 1 dia. of h P* the body. 

23 27. The 6th fat. 4 of the projection p. the edge or very 

near 1 dia. of 1 ? p. the body. 

o 1 5. The 6th fat. 4 dia. of t? p. the body. 

,0 58. The 6th fat. is ftill clear of the p. arm. 

x 16. The 6th fat. 4 dia. of j? p. the body; a very little p. 

the edge of the ring, and a little north. 

Nov. 3. 22 3. The p. arm is loaded in two places, at the far 

end and about the middle (F.) 

23 54. There feems to be a fatellite clofely following the 

' *f ft (G). 

/ - r.\ 

ll 

(C) 9 si ». aS o°,9- 9' 6 3*- H4°,9- 

(E) 6 46 3. 284,7. 

(F) They were the ift and 6th fatellites. See ift fat. Nov. 3* 

{G) 8tu S 1 ' 2io°, 5. 


O 10* 


Satellites of the Vianet Saturn . 471 

o 10. The diftance between the two fatellites upon the arm 
Is half the dia. of the fmalleft. 

Nov. 4. 22 1 7. The 6th fatellite 4 dia. of t?. f- the body (H). 

23 48. The 6th about J or 4 dia. of t? following the body.- 

Nov. 7. 21 28. The 6th towards the end upon the f. arm (I), 

22 39. The 6th is drawn a little nearer towards J? - 

Nov. 8. 20 46 The 6th about | dia. of \ f. hazy weather*. 
1 do not fee it well enough to eftimate its diftance very exactly*. 

21 16* The 6th fat. 4. dia. of the body. 

22 2. The 6th fat. 4 dia. of ^ f* the body. 

23 40. The 6th fat. 14 dia. of t? f. the body (K). 

Nov. 9. 21 42. The 6th fat. 4 dia. of t? p. the body, andJ 
a little north (L)~ 

Nov. 10. 2 33. The p. arm, near the end, feems to con- 
tain a fat. probably the 6th. 

21 39. The 6th full 4 dia. of ^ p* the body; almoft intirely 
to the fouth of the arm (M). 

22 28. The 6th is clear of the p. arm, and Is about 4 dia* 
of t? p. the body. 

23 27. The 6th almoft 4 dia. of P* the body. 

o 10. The 6th fat. 1 full dia. of vp« the body. 

Nov. 13. 22 33. The 6th fat. on the p. fide (N); 

Nov. 15. 22 33. The 6th fat. about 1. dia. of r ? . f. the: 
body (O). 

Nov. 19. 21 55. The 6thTat. 4 dia; of t? f • the body (P). 


y ij 

O 

> u 0 

(H) 7 11 6. 

94,8. 

(I) 6 10 28. 151,9.- 

(K) 8 18 11. 

78,0. 

(L) 6 16 34. 318,7. 

(.M) 6 9 39. 

220,1. 

(N) 6 51 44. 296,0. 

(@) 6 43 53 

100,0. 

(P) 5 50 17 - 6l > 1 * 


Novv 


- D r . -Herschel’s Observations on the 
Nov. 21. O 54. The 6th at a little dift. p. the edge of the 
ring (Q) 5 cloudy weather. 

• Nov. 25. 1 21. The 6th about % dia. of J? following the 
body (R). 

1 27. The 6th about \ the projection preceding the edge of 


the projection. 

, Nov. 26. 22 22. The 6th near 1 dia. of T ? f. the body (S). 

• o 20 Very nearly in conjunction with the 4th. 

Nov. 30. 23 47. The 6th full ’ dia. of * f. the body; 

about 2 \ dia. of the 3d fat. p. the 3d (T). 

Dec 2. 22 49. The 6th about % dia. of i; p. the body ; about 

1 dia. of the ift f. the ift- ■ . 

2 3 3^* The 6th fat. is paft its conjunction with the ift, 

which it now precedes. 

o 22. The 6th, the ift, and 3d fatellites, are nearly at equal 

diftances from each other. 

o 52. The 6th fat. nearly 1 dia. of \ p. the body (V). 

Dec. <• o 8. The 6th fat. f projection p. the arm (W). 
d“. » 35. The 6th about I dia. of 6 ft the body, and 

a little north (X). 

Dec. 1 6. 23 59. The 6th full 4. dia. of i ? p. the body (Y). 
Dec. 24. o 5. The 6th fat. 14- dia* of \ p. the body 5 or i| 

projection p. the edge of R. (Z). 


(Q) 

8 

■r 

40 

// 

57 * 

257.8- 

(S) 

5 

49 

44 * 

100, ii 

0 \ > \ 

(V) 

7 

55 

46/ 

2 >9 ? 4 * 

(X) 

6 

47 

48.. 

62}Or 

(Z) 

$ 

42 

3 S (; 

254 ^ 


- L 

(RJ 8 52 10. 230,7. 

(T) 6 58 48. 83,6. 

(W) 707- 3 1 7 a 3 - 

(¥■) 6 7 S8‘ 3 I 7 . 3 - 



Qbfervatiens 


Satellites of the Planet Saturn. 


♦ 


473 


Obfervations on the feventh fatellite of Saturn . 

Sept. 8. 22 51. The firjl fatellite f the dia. or a little lefs of 
the projection ff. R. (A). 

Sept. 14. 1 29. A fuppofed 7th fat. exceffively faint, § pro- 
jection p. R. exactly in the line of the R. fainter than the laft 
new one. 

1 46. The fuppofed 7th half a projection p. the R. (B). 

Sept. 17. 21 o. A fecond new fatellite exceffively faint, f 
projection p. the edge of the R. (C). 

22 55. The new, or 7th fat. J projection p. R. fo exceffively 
fmall that, if I had not feen it before, it would have been 
irnpoffible to perceive it now. 

(A) Not being acquainted with more than fix fatellites, and having the 2d, 3d, 
4th, 5th, and 6th in view, it was natural enough to call the remaining one, on 
which this obfervation is made, the ill; but from the note M of the ill fat. it 
appears, that it could not be in the place where this was feen ; and by calculating 
from the tables of the 7th fat. we have its place for nh. 28' 45". io6°,o, 
which agrees exa< 5 Hy with the fituation pointed out. From a figure, it appears, 
that the fat. was extremely fmall, and lefs than half its diameter fouth of the 
dine of the R. 

(B) I was now on the look-out for very fmall flars that were in any fituation 
likely to be fatellites of T? , and always noticed them : for inftance, <s Sept. 11. 
li 20 h. 42'. A fuppofed 7th fat, exactly in the line of the R. or a very little 
4 1 fouth, exceffively faint, only to be feen when I hide b by the field bar. Sept. 

“ H- 20 h. 40'. The 7th of Sept. 11. is left in its place.” So here this fup- 
pofed 7th is marked down, and Sept. 16. 20 h. 13' I find it is laid, that “ the 
44 fuppofed 7th of the 14th is a fmall fixed liar, left in the place where it was that 
46 evening; but as the configuration of liars which pointed out this fuppofed 7th 
was very eoarfe, and hardly fufficient to determine the place, and as by calculation 
it appears, that the 7th fatellite was in thd fituation where this obfervation places 
it, at 13 h. 59' 43", viz. 278^2, it is probable enough, that I favv thereat 
Satellite this evening. (C) 9 b. 2' 43". 265°,6, 

Vol. LXXX. Qqq 


2 0 


a ~ a Dr. Hersciiel’s Observations on the 

*T / i 

23 x. After a more attentive obfervation and hiding the pla- 
net, 1 fee the 7th fat. is not lefs than \ projection p. R. 

23 31. Forty-feet refleCtor. I fee fix fatellites at once, and 
being perfectly affured that the 2d is invifible, it becomes evi- 
dent that Saturn has feven fatellites^ This new fat. is ex- 
ceffively fmall. 

Sept. 18. 22. 4. The new fat. near 1 projection p. R. and 2 
little fouth, but fo faint that 1 hardly perceive it (D). 

22 36. I cannot perceive the new Satellite with the utmoft 
attention (E). Indeed it was fo faint before, that I almoft 

entertained a doubt of its reality. 

■ Sept. 25. 23 48. The 7th fat. I believe is between the 6th 

and the R. or J- projeftion f. the edge (F). 

23 52. I fee it very plainly 5 it is much fmaller than the 
6th; I have many times this evening before fufpeCted it, 

but the weather has been too hazy. 

Oa. 12. 22 6. 'The Jixth fiat . (G) dole to the f. projection, 

and a little north. 

22 13. I fee the fixth fat. very well ; but the projection is 
too faint to eftimate the diftance by it with any accuracy. 

22 24. The fixth being nearer to Saturn on the f. fide than, 
the 1 ft on the preceding, muft be quite clofe to the f. pio- 
jeCtion, or touching it. 

- 0>) io h. 2' 37". 3 ofs- 

(E) From the calculated place 10 h. 34" 32". we fee > rtiat the fatel * 

Site was drawn upon the arm, and therefore might eafily be overlooked, efpecially 

as its -revolution was unknown, 

(F) 11 h. 1 8' 48". I I 7 0 , 9. 

(G) The fatellite is here called the 6th, and we have feen before, in the note 
(S) of the 6th fat. that the 6th was called the 7th ; but the tables of thefe fatel- 
Hres leave no doubt to which of them the obfervations belong, 

oa. 


Satellites of the Vianet Saturn . 4^ 

Oft. 12. 23 35. The fixth fat . 1 projection, or perhaps a 
little lefs, f. the body ; I fee it with great difficulty, but have 
no doubt (H). 

1 8. I fee nothing of the fixth (I). 

Oft. 16. 20 23. The 7th fat. \ projection f. the body ; that 
is, the fat. is upon the middle of the arm (K). 

20 36. The 7th a little more than \ projection f. the body; 

extremely faint. 

20 50. The 7th fat. 1 of its own dia. f. the body of i? . 

21 11, The 7th is very nearly in contaft with the body. 

21 15. I can ftill perceive the 7th fat. by means of the field 
bar hiding the planet. 

21 55. The 7th is gone. 

1 29. I have a ftrong fufpicion of a fat® upon the p, pro- 
jection not far from the end of it (L). 

Oft. 18. 21 25. I am pretty fure the fat. is about 1 of its 
own dia. p. i? (M). 

21 26. Very clear. I fee the 7th fat. very plainly. 

21 35. About 2 of its own dia. from the body of i? , and a 
little north of the R. 

21 43. The 7th fat. f projection p. the body. 

21 51. The 7th fat. \ dia. of t? p. the body. 

22 26. The 7th fat. \ dia. of t? p. the body. 


(H) The calculated place 9b. 59' 10" in°,2, gives the fatellite farther 

from the arm than the obfervation ; but as this alfo mentions the fat. was feen 
with difficulty, the interval might appear lefs than it would have done in a very 
clear view of the fat. 


(I) The leaft change in the atmofphere would make the fat. invifible; and by 
the tables it alfo was now very nearly going upon the ring. 


(K) 6 31' 59. 144,4. 
(M) 7 25 58. 202,7. 


h - , 

( L ) 11 37 


// 

9- 


225,3. 


Q qq 2 


22 40. 


Dr. Hekschel’s Cbfervations on the 

22 4c. The 7th feems frill to be where it was. 

2 , j-.. The 7th approaches to a conjunction with the 6th. 

2 2 07, The conjunction of the 7th and 6th iatellites is paft. 
They are too near the planet to fee exadly how they are placed, 
o 20. The 7th fat. 4, or near dia. of J? p. the body, 
o 24. The 7th is clear of the projection . 
o 36. The 7th near \ projection p. the edge of the ring. I 

fee the R. well enough to eftimate by it. 

o 59. The ;th fat. f, or nearly 4, dia. of r? p. the body, 
j 2i. The 7th fat. 4 dia. of f? p. the body (N). 

Oft. 20. 21 26. I have a glimmering fight of the 7th fat. 

21 56. The 7th is perfectly detached from the p. arm. 

23 5. The fat. | of the dia. of % p. the body, or there- 
about. 

23 37. The 7th extremely faint, near 1 dia. of t? p. the body ; 
but the eftimation of the diftance is not very exactly to be had, 
as I am obliged to hide the planet when 1 fee the fat. There 
is a high wind, and the air being dry, the telelcope does not 

aft fo well as it did x \ hour ago. 

0 8. The 7th fat. % dia. of 1? p. the body ; or f (or nearly 1) 

projetion p. R. I fee the ring very plainly (O). 

1 o 20. The 7th fat. about | dia. of 1? p. the body. 

1 20. The 7th fat. about 4 dia. of i? p. the body. 

Nov. 4. 22 23. The p. arm feems to be loaded about 4 dia. 

of h from the body (P). 

Nov. 7. 22 o. The 7th fat. 4 dia, of % p. the body, ex- 
ceffively fmall ; but I fee it extremely well, and can keep it in 
view 1 it is juft following the ift and 2d fat. 


Satellite* of the Planet Saturn. 



12 9 - I fee the 7th extremely well, notwithftanding Its 
fmallnefs. ' 


22 39. The 7th about £ dia. of i? p. the body (Q). 

23 12. The 7th nearly the fame as at 22 h. 39', or perhaps 
a little nearer to ^ . 

Nov. 8. 21 17. The 7th is clear of the p. arm; but I do 
not fee it well enough yet to eftimate how much. 

22 o. The 7th fat. f dia. of t? p. the body (R). 

23 31. The 7th is upon the p. arm I fur-pole, for the wea- 
ther is now very clear, and I fee it no longer. There is a fmall 
protuberant point on the arm, which I take to be the latellite ; 
but, as it has been cloudy, I have not been able to follow it fo 
as to fee it go on fince 22 h. . 

23 40. I fee the 7th upon the arm. 

Nov. 10. 21 39. The p. arm is a little gouty, not quite r 
dia. of t? preceding the body (S) 

Nov. 15. 22 27. The 7th iau is clear of the f. projec- 
tion (T). 

22 39* The 7th fat. between the 6th and the projection of 
the R. and a very little to the north. 

22 44. The 7th confiderably lefs than the 6th ; I fee k how- 
ever very well, notwithftanding the difficulty of its fituation. 

22 56. By a figure, at a confiderable diftance following. 

Nov. 16. 22 50. The 7th lefs than 1 dia. of the iff fol- 
lowing the firft, and a little north (V). 

Nov. 29, o 38- A fmall luminous point on the f. arm fWL 


(Q) 7 si 16. 281,4. 

(S) 6 9 39. 328,5. 

C v ) 6 56 55. si2,8,. 


(R) 6 38 27. 291,9. 

( T > 6 37 54* 85 , 7 . 

< w ) 7 53 35- 53,3- 


Dee, 


■ s DA Herschel’s Obfervations on the 

Dec. 2. 23 38. I fufped the 7th to be juft detached from the 

f. arm (X). . . 

o 24. I cannot fee the 7th, though I tried often for it. 

o 56. The 7th fat. is not vifible. 

From the obfervations on the feven fatellites of Saturn that 
have been here delivered, and clofely compared with their calcu- 
lated places, it appears evidently that the revolutions of thefe 
fatellites are fo well afcertained, that we may, without hefitation, 
determine that no phenomenon on the ring of Saturn, m the 
lhapeof lucid fpot, protuberant point, or latent fatellite, can be 
occafioned by any of them, when, upon computation, we find 
that the place of the fatellite differs from that where fuch 
appearances were obferved. In conference of this deduction, 

I found, that the obfervations, which will be given prefently, 
could not be explained by any of the known fatellites ; it 
remained, therefore, to be examined to what caufe to afcribe 

the appearance of fuch lucid fpots. 

The firft idea that occurred was that of another fatellite, lull 
clo fe r to the ring than the feventh ; and if a revolution, flower 
than about 1 5 hours and a quarter, could have been found, 
which would have taken in the moft material places in which 
bright fpots were feen, I fhould have continued of opinion 
that an eighth fatellite, exterior to the ring, did exift, notwith- 
standing more obfervations had been wanting to put the matter 
out of all doubt. But this being ineradicable, I examined, 
in the next place, what would be the refult if thefe fuppofed 
fatellites, or protuberant points, were attached to the plane or 

edge of the ring. 


(X) 6h. 41' 59 ". ioo°, o. 


As 


Rotation of the Ring of Saturn. 

As obfervations, carefully made, fhould always take the lead 
of theories, I fhall not be concerned if fuch lucid Ipots as I 
am now going to admit, fhould feem to contradidt what has 
been faid in my laft Paper, concerning the idea of inequalities, 
or protuberant points. We may however remark, that a lucid, 
and apparently protuberant point, may exift without any great 
inequality in the ring, A vivid light, for inftance, will feem to 


project greatly beyond the limits of the body upon which it is 
placed. If therefore the luminous places on the hop- fhould 
be fuch as proceed from very bright reflecting regions, or, 
which is more probable, owe their exigence to the more fluc- 
tuating caufes, of inherent fires adting with great violence, we 
need not imagine the ring of Saturn to be very uneven or 
diftorted, in order to prefent us with fuch appearances as will 
be related. In this fenfe of the word, then, we may ftill 0 p- 

pofe the idea of protuberant points, fuch as would denote- 
immenle mountains of elevated furface. 


On comparing together leveral obfervations, a few trials 
fhew that the brighteft and beft obferved fpot agrees to a revo- 
lution of io k 32" 15 ",4 ; and, calculating its diftance from 
the center of Saturn on a fuppofition of its being a fatellite, we 
find it ly ,227, which brings it upon the ring. It is there- 
fore certain, that unlefs we fhould imagine the ring to be fuffi- 

eiently fluid to permit a fatellite to revolve in it, or fuppofe a 

notch, groove, or divifion in the ring, to fuffer the fatellite to 
pafs along, we ought to admit a revolution of the ring itfelf. 

The denfity of the ring indeed may be fuppofed to be very 
inconfiderable by thofe who imagine its light to be rather the 
effedt of fome fhining fluid, like an aurora borealis, than a 
refledtion from fome permanent fubftance ; but its difapparition 
m general, and in my telefcopes its faintnefs when turned edge- 
ways,, 


j 


4 g 0 Dr. Herschel’s Obfervations on the ■ 

ways, are in no manner favourable to this idea. When we 
add alfo, that this ring cafts a deep lhadow upon the planet is 
very Iharply defined both in its outer and inner edge, and m 
bright,, eft etc.ed, the plane, i.felf, it feems to be ataoft 
proved, (hat its confidence cannot be lefs than that o >e 
body of Saturn ; and that confequently, no degree of fluuhty 
can be admitted fofficient to permit a revolving body to keep in 

motion for any confiderable time. 

A groove might afford a paffage, efpecially as on a former 
occafion we have already confidered the idea ot a divided ring. 
A circumftance alfo which feems rather to favour tins idea is, 
that, in fome obfervations, a bright fpot has been feen to pro- 
ied equally on both Tides, as the fatellites have been obferved 
lo do when they pafled behind the ring. But, on the other hand, 
we ought to confider that the fpot has often been obferved very 
near the end of the arms of Saturn’s ring, and that the cal- 
culated diftance is confequently a little too fmall for fuch p- 
pearances, and ought to be 19 or zo feconds at leaft. _We 
Ihould alfo attend to the fize of the fpot, which feems o be 
variable; for it is hardly to be. imagined that a fatell.te, 
brighter than the fixth, and which could be een wit t e 
moon nearly at the full, fhould fo often efcape our notice in its 
frequent revolutions, unlefs it varied much in its apparen 

brightness. ^ ^ anQther argument drawn from the 

number of lucid fpots, which will not agree with the motion 
of one fatellite only; whereas, by admitting a revolution of 

the ring itfelf, in 10 h. 32' <> 4 ? and ^PP ofi Ȥ a11 th ! 
to adhere to the ring, and to fhare m the fame periodica 

return, provided they laft long enough to be feen many times 


Rotation of the Ring of Saturn, 48 1 

wc fliall be able to give an eafy folution to all the retraining 
obfervations. 

For inftance, let / 3 , 7, S, s, reprefent five fpots on the ring of 
Saturn, iituated as in fig. 2. ; where the ring is fuppoted to be 
divided into 360 degrees, and the foot a placed at 271°, 5 ; /3 at 
po : ,2 ; 7 at 183°, o ; $ at i42°,5 ; and e at 358°,6. Then will 
the ring, with the fpots thus placed, ferve as an epocha for the 
year 1789; by which, with the affidance of a table con» 
ftru&ed upon the before -mentioned period of the rotation of 
the ring, we may calculate their fit nation for any required 
time ; and to render this calculation perfectly convenient, I 
have given a table, ready prepared for the purpofe, at the end 
of the other tables. j 

The following obfervations have all been previoufly cal- 
culated by the tables of fuch of the feven fatellites as were 
not already in views and have been found to belong to neither 
of them; but in the notes that are given with them they have 
been again calculated by the table of the rotation of the ring for 
every time they were obferved ? on a fuppOfition of their being 
fpots adhering to it. 


Obfervations not accounted for by fatellites « 

* . ' \ 

\ . 

July 28. 22 31. I now perceive between the neareft fat. and 
T? , on the f. fide, a fmall lucid point, like an emerging fatel* 
lite (A). 

22 37. 

(A) My furmife of its being an emerging fatellite fo early as the beginning 
of the feafon, when I was ftill unacquainted with the minute phenomena that 
offered themfelves afterwards, fliews plainly, that the lucid point was of a fuiti- 
cient brightnefs to deferve notice. The five old fatellites were in view, and the 

Vol. LXXXo R r r 6th 


4 3 2 Dr. Herschei/s Ohfervations on the 

22 37. The laft difcovered point, not quite half-way be- 
tween the 3d fat. and the body of Saturn ; may be it is a 6th 
fat. By a figure,- the greateft part of its diameter is to the 
north of the ring (B). 

Aug. 29. 23 i. The preceding projection contains a fmall 
inequality. By a figure, it follows the 3d fat. about f of the 
projection of the ring (C). 

Sept. 16. 19 39. I fufpeCt one of the fatellites clofe to the 
ring following (D). 

20 6. I am pretty fure there is a fatellite clofe to the following 
arm, and a very little to the north. 300 leaves it doubtful (E), 

OCt. 15. 20 58. I fufpeCt a fatellite upon the preceding pro- 
jection, not far from the end of it (F). 

21 39. I cannot perceive the fatellite on the preceding arm 
fufpeCted at 20 h. 58 7 (G) . 

6th and 7th by calculation could not occafion this appearance, the former being 
at 7 2 0 , 3 ; the latter on the oppofite fide at 299°,4. Suppoiing this, therefore, to 
be the fpot I have called a, its place for 13I1. 53' 39" would be 3638; which 
might make it appear like an emerging fatellite. 

(B) By this time the fpot was at 40 ,3, which agrees with the obferved fitua- 
tion. As the greateE part of its diameter appeared to be north, we may furmife, 
that the fpot, which mult have been of a very confiderable fize and brightnefs, 
was fituated on the northern plane of the ring, and within a fecond or two from 
the outward edge of it. The ringitfelf was now fo near having its edge directed 
towards us, that it required no great elevation of the fpot to render it viiible,. 
notwithftanding it was then in the fartheft part of its circuit. 

(C) The fpot a, at 12 b. 1 Y 5.8 v was 301°, 5. 

<D) The fpot 0, at 7 h. 45 7 52" was 58°, 1. This fpot was probably alfo om 
the northern plane, and on the very edge, but notfo conliderable as ou 

(E) It was now advanced to 73°,4. 

(F) The fpot 7, at 7 h. io' 49" was 305°, 0. Its lituation on the ring was 
probably on the fouthern plane, and at fome conliderable difiance from the 
outward edge. 

(Gj It was now advanced to 328T3 ; and therefore could hardly be feen any 
longer, 

on. 


Rotation of the Ring of Saturn . 48 3 

OS. 1 6« 1 29. I was not without a fufpicion of another 
fateliite upon the preceding arm, not quite 1 o far advanced as 
the former (H)« 

Odl. 18, 20 22. I fufpedt two fatellites upon the p. arm (I). 

20 42. I make no doubt but that there is at leaft one fat. 
upon the p. arm (K). 

21 14. I am in doubt whether it be a fat. upon the p» arm, 
or the arm itfelf (L). 

21 17, Uniefs the p. arm be much brighter than the f. one, 
it mult contain a fateliite (M). 

j. 

I 1, I am pretty fare the end of the preceding projedlion is 
loaded with two fatellites. By a figure, one is placed | pro™ 
jedfcian from the end ; the other, f projection from the 
body (N) . 

Odl. 18. 1 5. I can diftinguiOi one upon the preceding pro- 
jection very certainly (Q). 

Odl. 20. 2i 26. I fufpedt the end of the preceding arm to 
be loaded with a fateliite (P) 

(H) The fpot / 3 . By calculation, at iih. 3^' 9" it was 309 c ? 2, or juft fol- 

lowing the 7th fateliite, which appeared then upon the preceding arm in the fhape 
of a fmail bright point. r 

( I ) The fpots y and The former at 6 h. 23' 9" -was 2I7°,6, the latter 

289°, 9. $ is probably a fpot upon the northern plane of the ring of a conli- 

■derable degree of brightnefs, though but fmail in its dimenfions, and at no great 
diftance from the edge. 

(K) The fpot y was by this time at 22 ^°,o } and therefore in a f tuation to be 
■eafily perceived. 

(L) The fpot y 247°, 2. (M) The fpot y 248°, 9. 

(N) The fpot a, at 1 1 h. 1' 23^, was at 217b 2 ; and £ was alfo vifible, being 
at 304°, 3. This fpot is probably a very fmail one, on the northern plane of the 
ring, at feme diftance from the edge. 

(O) The fpot « was now r at 21934, and being very bright could be diftin- 

gyiiflicd eafily. (P) The fpot «, at 7 h. 19'' 7", was at 290°, 7. 

R rr 2 


21 ^6. 


484 


Dr. Hersciiel’s Obfervntions on the 


21 56. The preceding arm is certainly loaded with one or 
two fatellites, or is more knotty than I have everobferved it to 
be. The weather is very beautiful (Q). 

Oft. 30. 20 53. I fuppofe the 7th to be upon the following 

arm J dia. of \ f. the body (R). 

22 55. The 7th fat. 4 dia. of t? p. the body, or very near to 
the end of the p. arm, in the fhape of a protuberant point (S). 

o 1 . 1 fee it fo well that there is no doubt but that it is a 

fatellite (T). 

o 42. The 7th is upon the p. arm, but a little nearer than 
it was before (V). 

o 47. The 7th fat. 4 dia. of t? p. the body (W). 

061 . 31. 21 13. The 7th fat. 4 dia. of t ? p. the body (X). 

21 43. The 7 th fat. is brighter than ufual; I fee it with 
great eafe, notwithftanding the moon is almoft at the full. It 
is brighter now than the 6th (Y ). 

22 1 1. The 7th is drawn nearer to the body of f? . Flying 
clouds prevent eftimations of the diftance (Z). 

23 13. The 7th is now no longer vifible (A). 

Nov. 2. 22 14. The 7th fat. 4 dia. of i? p. the body, it is 
•upon the arm (B). 

(QJ The fpot a was now at 30738 ; and at the fame time the fpot & being 
come on as far as 2 19°, 3, was therefore vifible. 

(R) The fpot i, at 6 h. 6' 57" was at 4033. 

(S> The fpot «, at 9 h. 8' 28", was at 2 7 2°, 4. 

(T) It was now at 275 °> 8 . 

(V) At 299°, u (W) At 30230. 

(X) The fpot «, at 6h. 22' 59", was 27834. 

(Y) It was now at 295 0 J5 ,, 


(Z) At 30537- 


(A) At 34637. 


(B) The fpot i, at 7 h, 15' 58", was at 23536. 


4 


22 53. 


Rotation of the Ring of Saturn . 485 

22 53. The 7th appears to be full J dia. of 3 p. the body; 
but hazy weather (C). 

23 13. The 7th fat. J dia. of J? p. the body (D). 

o 8. The following arm contains a lucid point near the end 
of it (E). 

o 16. The preceding arm feems to be loaded with two fmall 
points towards the end (F). 

Nov. 4. 22 14. The fib. fat. I think, is between the ift 
and 6th, but I cannot be fure (G). 

22 27. I cannot perceive the 7th fat. where I fufpedted 
it (H). 

23 47. The £ arm about J dia. of ^ from the body contains 
a fmall lucid point (I). 

23 54. I fee the point on the £ arm fo well that 1 have not 
much doubt but that it is a fatellite (K). 

Nov. 7. 22 9. At the end of the p. arm is a place that is 
brighter than nearer to the body (L). 

23 12. The preceding arm has frill the appearance of a 
fmall protuberant point towards the fouth, near the end of 
the arm (M). 

Nov. 8. 23 40. There is a protuberant point on the preceding 
arm hefides the 7th fat. ; fo that at prefent I cannot tell whe- 
ther the fatellite be the neareft or fartheft of them (N). 

(C) At 257°.8. (D) At 269°, 1. 

(E) The fpot at 84°, 4. (F) The fpot s, at 3053°* 

(G) The fpot at 7 h. 8' 7", was at 71 0 , o, which agrees with the place,, 
and it might be the fuppofed fatellite. (FI) At 7833* 

(I) The fpot at 8 h. 40' 51", was at 36°, 7. 

(K) It was now at 4037, 

(L) The fpot at 6h t 31' 21", was at 274°,^* 

(M) It was at 30938. 

(N) The fpot at 8 b. 18' si", was at 29434* 


Nov* 


4S6 Dr. He Rachel’s ' Obfervations on the 

Nov. io. 21 35. The following arm \ dia. of i? from the 
body contains a bright point ; perhaps an 8th latellite (O). 

Nov. 25. 1 2i. The p. arm is loaded (P). 

Nov. 20. o 38. There are two fmall luminous points on the 

p. arm (Q). 

Dec. 5. o 8. Upon the end of the p. arm appears to be a 
bright point (R). 

0 10. The fpot on the preceding arm is rather larger than 
the 6th fateliite (S). 

Dec* 16. -o 7. The end of the p. arm feems to be loaded, 
with a fateliite (T). 

/Dec. 24. o 7. The p. arm contains a pretty bright point J 
to wards the end of it (V). 

Dec. 25. 23 39. The p. arm very near the end is loaded 
%vith a fat. (W). 

1 10. The p. arm is loaded very nearly at the far end of it, 

and a little towards the fouth (X). 

1 37. The bright point is near the far end of the p. arm (Y). 

The great accordance between the obferved places of thefe 
{pots and the calculated ones, feems to eftablifh the rotation of 
the ring of Saturn on an axis fo as hardly to leave any doubt 
upon the fubjeft. The time of it, we have already feen, is 
io hours, 32 minutes, and 15*4 Seconds. It may be objected, 

(O) The fpot at 6h. 5' 40", was at 59°, 1. 

(P) The fpot £ , at 8h. 52' 10", was at 68°, 6. 

(QJ The fpot 0, at 7 h. 53' 35", was at 259°, 6. 

(R) The fpot at 7 h. o' 7", was at 283° 5 8. 

(S) „ It was now at 285°, o. 

(T) The fpot e, at 6 h. 15' 57", was at 27 7 0 , 4. 

(V) The fpot a, at 5 h. 44' 33", was at 25i°,6. 

,(W) The fpot 0, at 5 h. 12' 42", was at 244°, 8. 

*X) It was now at 296°, 0. (Y) And now at 31144. 

that 


1 


Rotation of the Ring of Saturn. 4^ 

that many of the observations are fuch as would alfo agree with 
other affignable periods, efpecially when the numbers of fpots 
is lo confiderable as five ; but the rnoft material obfervations 9 
which are thofe on the fpot a v fetting afide all the reft, feem 
alone to amount to a proof not only of a rotation of the ring* 
but of the time in which it is performed. 

( 

It may be expected, that having now fufficiently examined 
the whole feries of obfervations of the laft new fatellites, we 
oa 1 give then peiiochcal times and diftances more accurately 
than before. The times, indeed, are full as well afcertained 
as we can expeft to have them : for on calculating fix fatellites 
by my tables back to Aug. 19 d. 12 h. 19' 56", 1787, we find 
their places 341°, 1 the 5th; ro\6 the 4th ; 211°, 1 the 3d ; 

1 58', 9 the 2d; 8 o °, 2 the n't; and 288’, 8 the 6th. And 
journal contains the fulleft aflbrance that they were thus 
lituated at the time for which this calculation is made. We 
ma y therefore fix the period of the fixth at x d. 8 h. 8 // ,p 
The 7th fatellite can only be traced back as far as the 8th of 
Sept. 1789; fo that its revolution will require at leaf! ano- 
ther leafon to come to forne degree of accuracy, till when we 
fhall ftate it at 22 h. 3 7' 22", 9. 

The difiance of thefe fatellites, N deduced from calculation, 
depends intirely upon the time and diftance of the 4th, which 
is the fatellite that has been ufed. In order to obtain more 
accuracy m thefe elements, I have applied myfelf to mea- 
ning the difiance of the 4th fatellite in thofe moments which 
were moft favourable for the purpofe. It is well known that 
this fubjetl, on account of the quantity of matter in Saturn, 
to be deduced from the periodical times and diftances of the 
fatellites, is of confiderable importance to aftronomers ; I fhall 

7 therefore 


4 gg . Dr. Herschel’s Tables for the 

therefore defer a full inveftigation of it till I can have an oppor- 
tunity of calculating a great number of meafures, not only of 
the 4th and 5th, but all'o of the other fatellites which I have 
a l read v by me, and ftill intend next feafon to take. Mean 
while, having brought the meafures of the 30th of November, 
which feern to me to be very good ones, to the mean diftance of 
Saturn from the fun, i find tnev gtve the dntancc of the 4th 
fatellite from Saturn 3' 8^,9 18. In reducing thefe meafures to 
the mean diftance, I have ufed the new tables of M. de 
La mb re for Saturn, and Mayer’s for the fun. 

Admitting therefore the above quantity as she diftance, and 
i sd. 22 h. 41' 13'', 4 as the period of the 4th fatellite, we 
compute that the diftance of the 6th fiom the centei of Sa- 
turn is 3^ ^,7889 » and that of the ^th, 28 ,6609* 


- — 

Tables for the feven fatellites of Saturn. 


Epochs of the mean longitude of the fatellites. 



5. fat. 

4. fat. 

3. fat. 

2. fat. 

I. fat. 

6. fat. 

A -> 

r^- 

Years. 

Deg.dec 

Deg. dec. 

Deg. dec. 

Deg. dec. 

Deg. dec. 

Deg. dec. 

Deg. dec. 

1787 

1788 

1789 
179° 

i 1 79 I 

335 ? 9 1 
196,84 

■ 53.23 

209,63 

126,02 

149,16 

132,41 

93>°9 

53=77 

14,45 

87,21 

93-86 

20,82 

3 ° 7 > 7 S 

234>74 

272.18 

173.95 

304.19 

74*43 

204,68 

176,46 

256,66 

21,41 

146,16 

269,31 

307,48 

82,92 

218,36 

353 > y 1 

307,07 

65,02 

161,00 

256,98 

352.97 




Saturnicentric 


Seven Satellites of Saturn . 



Saturnicentric motion of the fateilites in months. 



5th. 

4th. 

3 d - 

2d. 

ift. 

6th. 

7th. 

Months 

Deg. dec 

Deg. dec. 

Deg. dec. 

Deg. dec. 

Deg. dec. 

Deg. dec. 

Deg. dec. 

January 

Februa. 

March 

000,00 

140,68 

267,75 

000,00 

339,89 

252,05 

000,00 

3 IO * 4 ° 

2 i ,73 

000,00 

”7,58 

200,56 

000,00 

151,64 

91,18 

000,00 

224,54 

20.91 

000,00 

320,81 

215,73 

April 

May 

June 

48,43 

184,57 

325,25 

23 D 95 

189,26 

169,16 

332,13 

202,84 

153,24 

318,14 

3 ° 4, i 9 

61,77 

242,81 

203,75 

355*39 

245*45 

207,27 

71,81 

176,54 

115,39 

76,20 

July 
a u gua 
Septem. 

101,39 

242,07 

22,75 

126,47 

106,37 

86,26 

23,94 

334,34 

284,74 

47,82 

165,40 

282,98 

316,33 

107,96 

259,60 

33,63 

258,17 

122,72 

I 5»°5 

335*86 

296,67 

October 
Novem. 
Decern . 

1 58,89 

299,57 

75,71 

4358 

23,47 

340,78 

J 55-45 

105,85 

33 6 ,56 I 

269,03 

26,61 

12,66 

220,54 

12,17 

333 ’ 1 1 

84,54 

309,08 

270,90 

235,52 

! 96,33 

135,17 


In the months January and February of a biffextile year 
fubtradl i from the number of days given. 


< 



t 


s ff 


Vol. LXXX. 


Motion 


Dr. Herschel’j Tables for the 


490 

Motion of the fatellites in days. 



5th. 

4th. 

3 d - 

2d. 

lft. 

6th. 

7 th. 

Days I 

)eg* Dec. I 

)eg. dec. I 

)eg. dec. I 

)eg. dec. I 

)eg. dec. I 

)eg. dec. I 

)eg. dec. 

1 

2 

3 

4)54 

9,08 

13,61 

22,58 

45, 15 
67,73 

79,69 

‘ 59 , 3 8 
239,07 

131,53 

263,07 

34,60 

190,70 
21,40 
2 12,09 

262.73 
165 45 
68,18 

21,96 

43.92 

65,88 

4 

.5 

6 

18,15 
22,69 i 
27,23 

9°5 3 1 
1 12,89 

‘35,46 j 

318,76 

3 8 >45 

Il8,I4 

166,14 

297,6: 

69,21 

42,79 
233 49 

64,19 

33 °- 9 ‘ 
2 <5.64 
136,36 

87.85 
109,8 1 

1 3 1 >7 7 

7 

8 

9 

3 1 ’7 7 

3 6 > 3 ° 

40,84 

> 

158,04 

180,62 

203,19 

‘ 97, 8 3 
277,52 

357 , 2 ‘ 

200,74 

332,28 

103,81 

254,89 

85,58 

276,28 

39>°9 

301,82 

204,55 

153,73 

175,69 

197,65 

10 

1 1 

12 

45 , 3 8 

49 > 9 2 

54.46 

225,77 

248,35 

270,93 

76,90 

‘ 5 6 59 

226,28 
l/ 7 

235^35 

6,8a 

138,42 | 

106,98 

297,68 

128,38 

107,27 

10,00 

272,73 

219.62 

241,58 

263,54 

1 3 

14 

15 

5 8 >99 

63.53 

68,07 

293,5° 

316,08 

338,66 

3 1 5,97 
35,66 

“ 5,35 

269,95 

4 3 ?49 

173,02 

3 3 9’°7 

* 49.77 

340.47 

■ 75,45 

78,18 

340,91 

285,50 

307,46 

329,42 

16 

*7 

18 

72,61 

77 , >5 
81,69 

1,24 

23,81 

46,39 

‘ 95, °4 
2 74.74 
354*43 

304,56 

70,09 

207,63 

I * 7 *»‘7 
1,87 

192,56 

2+3,64 

146,36 

49,09 

35 1 39 
1 3.35 
35 . 3 1 

19 

20 

21 

86,22 

90,76 

95 , 3 ° 

68,97 

9‘,54 

I 14,12 

74,12 
‘ 53,8 ‘ 
233 , 5 0 

339 ,‘ 6 

I IO.7O 
242,23 

23,26 

213,96 

44,66 

3“,82 
214 , 54 
117,27 

57> 2 7 
79 23 
101,19 

22 

23 

24 

99,84 

104,38 

108,91 

136,70 

159,28 

181,85 

3 I 3» I 9 

32,88 

112,57 

* 3.77 

3 45 ’ 3 ° 
j 276,84 

235,35 

66,05 

25 6 ,75 

20,00 

282,73 

185,45 

123, 16 
145,12 
167,08 

■ 2 i 

26 

27 

1 * 3.45 
1 17*99 
122,53 

204,43 
227,01 
249 ? 5 ^ 

1 12,26 

271.95 

35 3 764 

48,37 

179 , 9 ‘ 
3 “>44 

8 7,45 

278,15 

108,84 

88,18 
350,9 r 
2 53>64 

189,04 
21 1,00 
232,96 

28 

29 

3 ° 

127,07 

121,60 

136,14 

272,16 

294,74 

3 » 7 * 3 ^ 

71,33 

151,02 

230,71 

82,98 

2 H. 5 1 

346,05 

299,54 

130,24 

320,94 

156,36 

59, °9 
"321,82 

1 254,92 
1 276,89 
i 298.85 

3 1 

. 140,68 

339 8 9 

310,4° j 117,58 

‘j ‘,64 

224,54 

| 320,81 


M otion 


Seven Satellites of Saturn . 




Motion of the fatellites in hou 

JL OS 



5 th. 

4th. 

3 d, 

2d. 

1 ft. 

6th. 

7 th. 

Hours. 

Deg. dec. 

Peg. dec. 

Deg. dec. 

Deg. dec. 

Deg. dec. 

Deg, dec. 

Deg. dec. 

I 

0,19 

o,Q 4 

3 > 3 2 

5,48 

7,95 

10,95 

I 5 > 9 2 

o 

°,3 8 

1,88 

6,64 

10,96 

15,89 

21,89 

3 ', 83 

3 

' 0,57 

2,82 

9 96 

16,44 

23,84 

32,84 

47.75 

4 

0,76 

3,7 6 

13,28 

21,92 

3 1 > 7 S 

43>/9 

63,66 

5 

°> 9 S 

4.7° 

16,60 

27,40 

39,73 

54,73 

79,58 

6 


5> 6 4 

19,92 

32,88 

47, 6 7 

65,68 

95,49 

7 

*,32 

6,58 

2 3» 2 4 

38,36 

55,62 

76,63 

1 1 1,41 

8 

^51 

7.53 

26,56 

43,84 

63,57 

87,58 

127,32 

9 

1,70 

8,47 

29,88 

49’33 

7i, 5 1 

98,52 

143,24 

IO 

1,89 

9>4* 

33> 2 ° 

54,81 

79,46 

109,47 

15945 

1 1 

2,08 

io ,35 

3 6 )52 

60,29 

87,40 

120,42 

175, °7 

12 

2,27 

11,29 

39.84 

65,77 

95>35 

131,36 

190,98 

*3 

2,46 

12,23 

43. 1 7 

71,25 

103,29 - 

142,31 

206,90 

14 

2,65 

1 S’ 1 7 

46,49 

76,73 

1 1 1,24 

153,26 

222,8l 

*5 

2,84 

144 * 

49,81 

82,21 

119,19 

164,20 

238,73 

■ 

16 

3>°3 

*5>°5 

53,13 

87,69 

! 27, I 3 


254,64 

l 7 

3,21 

* 5>99 

56,45 

9307 

135,08 

186,10 

270,56 

18 

3 > 4 ° 

16,93 

59,77 

98,65 

143,02 

I 97,°5 

286,47 

19 

3^59 

17,87 

63, 0 9 

104,13 

I 5°>9 7 

207,99 

302,39 

20 

3 * 78 

18,81 

6b, 41 

109,61 

158,91 

218,94 

3 l8 , 3 ° 

21 

3>97 

19-75 

69,73 

i 15,09 

1 66,86 

229,89 

334,22 

22 

4,l6 

20,70 

73,05 

120,57 

174,81 

240,83 

35 °, ‘3 

2 3 

4?35 

21,64 

76,37 

126,05 

182,75 

251,78 

6,05. 

24, 

4,54 

22,58 

79,69 

13^53 

190,70 

262,73 

21,96 




S f f 2 


Motion 


49 2 


Dr. Herschel’s Tables for the 


Motion of the Satellites in minutes. 


5 th - 

4th. 

3 d * 

2d. 

lft. 

6th. 

7 «h- 

Min* . 

Deg. dec. 

Deg. dec. 1 

Deg. dec. 1 

Deg. dec. 

Deg. dec.. 

Deg- dec. 

Deg. dec. 

1 

2 

3 

0,00 

0,01 

0,01 

0,02 

0,03 

0,05 

0,06 
0, 1 1 
0,17 

0,09 

0,18 

0,27 

0,13 

0,26 

0,40 

0,18 

0,36 

0,55 

0,27 

0,53 

0,80 

4 

5 

6 

0,01 

0,02 

0,02 

o,c6 

0,08 

0,09 

0,22 

0,2S 

°,33 

. 0,37 

0,46 

o,55 

0,53 

0,66 

o,79 

o ,73 

0,91 

1,09 

1,06 

1 >33 
i ,59 

7 

8 

9 

io 

i i 
12 

• 

0,02 

0,03 

0,03 

O 03 
0,04 
0,04 

0, 1 1 
0,13 
o,i 4 

o,39 

0,44 

o, 5 ° 

0,64 

o,73 

0,82 

o,93 

1,06 

1,19 

1 ,28 
1,46 
1,64' 

1,86 

2,12 

2 ,39 

0,16 

0,17 

0,19 

o ,55 

0,61 

o,66 

0,91 

1,00 

1,10 

1,32 

1,46 

*,59 

1,82 

2,01 

2,19 

2,65 

2,92 

3,18 

13 

14 

15 

0,04 

0,05 

0,05 

0,20 

0,22 

0,24 

0,72 

0,77 

0,83 

1,19 

1,28 

i ,37 

1,72 

1,85 

1,99 

2,37 
2 ,55 
.2,74 

3,45 

S’7 1 , 

3 > 9 8 

16 

17 

18 

0,05 

0,06 

0,06 

0,25 

0,27 

0,28 

0,89 

0,94 

1,00 

1,46 

i. 55 - 

1,64 

2,12 

2,25 

2 , 3 8 

2,92 

3 , 10 
3,28 

4,24 

4 , 5 X 

4,78 

19 

20 
21 

0,06 

0,07 

0,07 

0,30 

o^ 1 

°>33 

1,05 
1, 11 
1,16 

i .73 

i 8 ° 

1 ,°d 

'i, 9 2 

2,52 

2,65 

2,78 

3,47 

3,6s 

3> 8 3 

5, °4 
5 > 3 X 
5>57 

22 

2 3 

24 

0,07 

O ,08 

0,08 

0,34 

0,36 

°, 3 8 

1,22 

1,27 

I ?33 

2,01 

2,10 

2,19 

2,91 

3,°5 

3,18 

4,01 

4,20 

4 , 3 8 

s> 8 4 

6,10 

6 , 37 

: 2 5 

26 

27 

0,08 

0,09 

0,09 

°>39 

0,41 

0,42 

i,3 8 

i ,44 

M 49 

2,28 

2.37 

2,47 

3 > 3 X 

3,44 

3,57 

4 > 5 6 

4,74 

4,93 

6,63 

6,90 

7,16 

28 

29 

3 ° 

o ,°9 

O, iO 

1 0,10 

0,44 

o ,45 

0,47 

55 

1,60 

1,66 

2,S& 

2,65 

2,74 

3,7i 

3» 8 4 

3,97 

5 , 11 
5’ 2 9 
5, 47 

7,43 

7, 6 9 

7>9 6 

_ • 


Motion 


Seven Satellites of Saturn, 


493 




Motion 

of the Satellites 

in minutes. 

! 


5 * 

4th. 

3 d 

2d. 

ill. 

6th. 

7til. 

Min, 

Deg. Dec. 

Deg. dec 

D^g. dec. 

Deg. dec. 

Deg:, dec. 

Deg. dec. 

Deg dec. 

3 1 

0,10 

0,49 

1,72 

2,83 

4,10 

5, 66 

8,22 

3 2 

on 

0,50 

D 77 

2,92 

4 , 2 4 

5.84 

8,49 

33 

0, 1 1 

0,52 

1,83 

3 > 01 

4,37 

6,02 

8,75 

34 

0,1 1 

o ,53 

1,88 

3 ,i° 

4,50 

6,20 

9,02 

35 

0, 12 

0,53 

x ,94 

3,20 

4, 6 3 

6-39 

9,29 

36 

Oj 1 2 

0,56 

1 >99 

3> 2 9 

4,77 

6,57 

9,55 

37 

0,12 

0,58 

2,05 

3 - 38 

4, 90 

6,75 

9,82 

38 

°j i 3 

0,60 

2, 10 

3>47 

5-03 

6,93 

10,08 

39 

°D 3 

0,61 

2,16 

3 ' 5 6 

5, i 6 

7,12 

IO >35 

40 

0,13 

0,63 

2)21 

3,65 

5 3 ° 

7 , 3 ° 

10,61 

41 

0,14 

0,64 

2,27 

3?74 

5,43 

7,48 

10,88 

42 

0,14 

0,66 

2,32 

3,83 

5 5 6 

7,66 

11,14 

43 

0,14 

0,67 

2,38 

3>93 

5, 6 9 

7,85 

11,41 

44 

0,15 

0,69 

2,43 

4,02 

5 83 

8,03 

11,67 

45 

0,15 

0,71 

2,49 

4,ii 

5 > 9 6 

8,21 

1 1,94 

46 

0,15 

0,72 

2,55 

4,20 

6,09 

8,39 

12,20 

47 

0,16 

o ,74 

2,60 

4,29 

6,22 

8,58 

12,47 

48 

0,l6 

o, 7 S 

2,66 

4 ? 3 ^ 

6 , 3 6 

8,76 

12,73 

49 

0,16 

o ,77 

2,71 

4>47 

6,49 

8,94 

13,00 

5 ° 

OD 7 

0,78 

2,77 

4,57 

6,62 

9 > 12 

x 3> 2 7 

5 1 

0,17 

0,80 

2,82 

4,66 

6,75 

9 > 3 ° 

. J 3>53 

52 

0,17 

0,82 

2,88 

4>75 

6,88 

9,49 

13,80 

53 

0,17 

0,83 

2,93 

4,84 

7,02 

9.67 

14,06 

54 

0,1 8 

0,85 

2,99 

4->93 

7 > 1 5 

9,85 

x 4>33 

55 

0,18 

0,86 

3>°4 

5,02 

7,28 

10,03 

* 4>59 

56 

o 5 i 8 

0,88 

3,!o 

5 Di 

7 , 4 i 

10,22 

14,80 

57 

°> x 9 

0,89 

3 D 5 

5,20 

7 >S 5 

10,40 

x 5 > 12 

58 

0,19 

0,91 

3,21 

5^30 

7,68 

10,58 

15,39 

59 

0,19 

o,93 

3,27 

5’39 

7,81 

10,76 

1 5> b 5 

60 

0,20 

0,94 

3?32 

5>4§ 

7,94 

10,95 

I5.Q2 


3 


Table 


Dr. Herschel’s Table for the 
Table of the rotation of the ring of Saturn. 


Motion of the fpots in days, hours, and minutes. 


Epochs for 

Spot co 
<3 

1789. ^ 

Days I 

Deg. dec J 

-Jou. J 

Deg.dec 1 

vlin. j] 

Deg.dec Min. Deg. dec 

271, 5 

183,° 
no. 2 

1 

2 

0 

0 

99 ’ 9 2 

[99,84 

299,76 

1 

2 

0 

0 

34 , >6 

68,33 

102,49 

1 

2 

O 

0 

c ,57 

M4 

1,71 

3 1 

3 2 
3 ^ 

17,65 

18,22 

18,79 

f / * 

$ 142,5 

* 358,6 

4 

r 

0 

6 

39 68 
139,60 

239,52 

4 

5 

t> i 

136.65 

170,81 

204,95 

4 

5 
b 

2,28 

2,85 

3’42 

34 

35 1 
3 b ! 

I Q . ,6 

1 9 > 9 3 
20,50 

Motion of 
in Moni 

Months. 

January 

February 

March 

the ipots 
:hs. 

Deg. ' dec. 

000,00 

217,52 

135,28 

7 

8 

9 

339>44 

79>36 

179,28 

7 

8 

9 

239,14 

273,30 

307,46 

7 

8 

9 

3,99 

4 - 5 ° 

5> 12 

37 

3 * 

39 

21,07 

21,64 

22,21 

10 

1 1 

12 

279,20 
19,12 
1 19,04 

10 

1 1 

1 2 

341,63 

i 5>79 

49,95 

10 

1 1 

12 

5,69 

6,2b 

6,83 

40 

41 

42 

22,78 

2 3’3 5 
2 3 > 9 J 

April 

May 

June 

J u| y 

Auguft 

September 

352,8° 

1 10,40 
327,92 

. 

85, 52 

3 ° 3>04 

160,56 

13 

H 

15 

2 18,96 
318,88 
58,80 

*3 

J 5 

84,11 
I ib,28 
! 5 2 >44 

13 

14 

15 

7,40 

7,97 

8,54 

43 

44 

45 

24,48 

25,05 

25,62 

■ 

16 

*7 

18 

158.72 

258,04 

358,56 

16 

17 

18 

186,60 

220,76 

2 54>93 

16 

17 

18 

9,11 

9,68 

10,25 

46 

47 
48* 

26,19 

26,76 

2 7 9 33 

October 

November 

December 

278,16 

135,68 

253,28 

J 9 

20 

21 

98,48 

198,40 

-98,32 

19 

20 

2 1 

289,09 

3 2 3> 2 5 
35 7 ? 4 1 

J 9 

20 

21 

> 

10,82 

n >39 

11,96 

49 

50 

5 1 

27,90 

28,47 

29,04 

/ 

22 

2 3 

/24 

38,24 

138,16 

238,08 

22 

2 3 

24 

3659 

65,75 

99,91 

22 

23 

24 

' 2,53 

13, 10 

13,67 

5 2 

53 

54 

29,61 
30, 1 8 
3°’ 7 5 

25 

26 

27 

338,0° 

77,92 

07,84 


25 

26 

2 7 

14,24 

14,80 

* 5>37 

55 

56 

57 

31,32 

3 1 > s 9 

32,46 

28 

29 

3 ° 

3 i 

277,76 
17,68 
1 17,60 

217,52 

28 

29 

3 ° 

• 5,94 

16,51 

17,08 

S8 

■ 59 
bo 

33, °3 
33>59 
34,16 





Example 



I 








/ 

' . •- 









Rotation of the Ring of Saturn 


Example of the ufe of the tables. 

Let It be required to calculate the apparent place of the 
feven fatellites for 1789, 0 &. 18. 7 h. 51' 54 ", to the nearelt 
minute of time and to tenths of a degree. 



5 th - 

4th. 

3 d - 

2Cl. 

ift. 

6th. 

^th. 

53» 2 3 

158,89 

81,69 

*» 3 2 

0,17 

12,58 

93>°9 

43 > 5 8 

46,39 

6 , 5 8 

0,82 

12,58 

20,82 

155,45 

354,43 

23,24 

2,88 

I2,j8 '• 

304,19 

269,03 

207,63 

3 8 > 3 6 

4>75 

12,58 

256,66 

220,54 

192,56 

55> 6 2 
6,88 
12 58 

82,92 

84,54 
49, °9 

76,63 

9,49 

12,58 

161,00 
235,S 2 [ 
35> 3 1 

111,41 

13,8° 

' 12,58 

3 ° 7’9 

203,0 

209,4 

- J 

116,5 

*24,8 

315,3 

209,6 


The fituation of the fpot a. calculated for July 28. 13b. 53 
j8 for Sept. 16. 7 h. 45' 48"'} £ for Nov. 2. 7 h. 15 58 



1789, a 
July 

28 

*3 

•54 

h 

271,5 

85,52 

277,70 

84,11 

3°’75 

7,20 

(3 I 

Sept. 

16 

7 

46 

h 

183,0 
160,56 
158,72 
259, H 
26,19 
10,45 

£ 

Nov. 

2 

7 

16 

h 

35 8 > 6 

135,68 

199,84 

239,14 

9 ,n 

13,18 


36,8 


58,1 


235 , 6 . 


* The quantity marked lj 12°, 58, which is applied to every one of the rate ites, 
is the complement of 11 s if 25', or geocentric place ot Saturn, taken rom 
the Nautical Almanac, for midnight of the required day, and to the neare t 
minute, which is iufficiently exaft. This complement,^ or 12° 35' m comoim 
with the tables, is reduced to decimals of a degree 12°, 5 s * 


I 





[ 49 6 3 


f 


XXIV. On Spherical Motion. By the Rev. Charles Wildborc ; 
communicated by Earl Stanhope, F. R. S. 


Read June 24, 1790. 

T HIS Paper, which has coft me much pains in patient 
inveftigation, is occalioned by that of Mr. Landen, in 
the Philofophical Tranfadions, Vol. LXXV. Part II. I am 
no ftranger to this gentleman’s great judgement and abilities in 
thefe abftrufe {peculations, but have a very high opinion of 
both ; yet I could not but think it ftrange, that two fuch ma- 
thematician^ as M. d’Alembert and M. L. Euler Ihould 
both follow one another on the fame fubjed, both agree, and 
Rill not be right. I therefore refolved to try to dive to the 
bottom of their folutions, which thofe who are acquainted with 
the fubject know to be no light talk ; and, if poffible, to give 
the folution, independent of the perplexing confideration of a 
momentary axis changing its place both in the body and in 
abfolute fpace every inftant ; and which I look upon as not ab- 
folutely effential to the determination of the body’s motion. 
But finding that I could not thus fo readily Ihew the agree- 
ment or difagreement of my conclufions with thofe of the gen- 
tlemen who have preceded me in this enquiry; I have alfo 
added the inveftigation of the properties of this axis. And I 
fuppole it will be found, that 1 have added many properties 
unknown before, or at leaft unnoticed by any of them. 

M. Landen’s 


Mr. Wildbore on Spherical Motion. 497 

M. Landen’s very important difcovery, that every body, 
be its form ever fo irregular, will revolve in the fame manner 
as if its mafs were equally divided and placed in the eight 
angles, or difpofed in the eight odlants of a regular parallelo- 
pipedon, whofe moments of inertia round its three permanent 
axes are the fame as thofe of the body, ferves admirably to 
fhorten the inveftigation, and render the folution perfpicuous. 
I have therefore here taken its truth for granted, becaufe it is 
alfo exactly agreeable to the folutions of the other gentlemen, 
and faves the trouble of repeating what they have done before. 
I have alfo (hewn wherein, and why, his folution differs from 
theirs, and proved, as I think, undeniably, in what refpects it 
is defective. * 

That the inertia, or, as M. Euler calls it, the momentum 
of inertia , is equal to the fluent or fum of every particle of the 
body drawn into the fquare of its diftance from the axis of 
motion ; and the determination of the three permanent axes, 
or the demonftration that there are, at leaft, three fuch axes in 
every body, round any one of which, if it revolved, the velo- 
city would be for ever uniform, I have alfo taken for granted, 

, becaufe thefe things have been proved before, and all the gen- 
tlemen are agreed in them. Difficulties that occurred I have 
not concealed, but {hewn how to obviate, and endeavoured to 
place the truth in as clear a light as pofiible ; which to difco- 
ver is my wifh, or to welcome it by whomfoever found. 

proposition 1. 

Whilft a globe, whofe centre is at reft, revolves ■ with a 
given velocity about an axis paffing through that centre, to 
Yol. LXXX. Ttt find 


498 Mr. Wildbore on 

find with what velocity any great circle on the furface, but 
oblique to that axis, moves along itfelf. 

Let I (Tab. XX. fig. i.) be the centre, and BL b the axis round 
which the globe revolves with a velocity = c meafured along the 
great circle GH, whofe plane is perpendicular to that axis, and 
HSGj any great circle whofe plane is oblique to the axis, ESF 
and esf two leffer circles of the Iphere parallel to the great cir- 
cle GH, and touching HSGr in S and s ; then, as the radius 
BI which may be fuppofed unity : c :: the radius of the lefs 
circle ESF = the fine of the arc BE or BS : the velocity along 
the circle ESF = the abfolute velocity of the point S on the 
furface of the globe : but the point S is alfo upon the great 
circle GSHr, and therefore this is alfo equal to the velocity of 
the point s along the great circle GSRf ; and for the fame 
reafons the point S, which is diametrically oppoliteto S on the 
furface, has alfo the fame velocity. Let P be any other point 
in the great circle GSHj; then, fince as the globe revolves the 
diftances SP and jP always continue invariable, the velocity of 
the point P in the circle HPS in the direction of the periphery 
of the circle itfelf muft be equal to that of S and s ; and is 
therefore the velocity of every point of this circle along its 
own periphery. 

Corollary i. Hence it follows, that in whatfoever manner a 
globe revolves, its velocity meafured on the fame great circle on 
its furface muft be the fame at the fame time at every point of 
the periphery of that circle. 

Corollary 2. Confequently, howfoever the plane of a great 
circle varies its motion, the velocity at any inftant is at every 
point of the periphery equal along its own plane. 

, / ( '■ •• . 


DEFI 


Spherical Motion . < 499 

definition. 

I 

The points S and s, where a great circle from the poles B 
and b of the natural axis cuts any great circle GSHr (at right 
angles) I call the nodes of that great cucle. 

Corollary 3. If O be the pole of the great circle HSGr, then 
the globe may be confidered as moving round the axis whole 

pole is O with a velocity — ex fine , whilft the pole O is car- 
ried along the leffer circle AOA, which is parallel to the mid- 
circle GH with a velocity = c x = c x — gp- , and tms 

way of confidering the motion, which is ufeful in what 
follows, comes to the very fame as the motion along the 
great or midcircle GH with the velocity = c, becaufe c' x 

B ' jI i. c z v C .°£ B 1 as Confequently, the fum of the fquares 
BI 2 ~ BI 2 ^ 

of the velocities at the node and pole of any great circle upon 
a fpherical furface thus revolving, is equal to the fquare of the 
velocity round the natural (or momentary) axis B lb. 

Corollary 4. Since the pole O is at 90° diftance from the node 
S, its motion can have no effe£t at S or s, the motion at the 
nodes, therefore, of the great circle HSGj is that of the great 
circle along its own proper plane ; but any other point, as P, 
partakes both of the motion along the circle, and the motion 
of its pole. The direction of its motion being along die le ~r 
circle P/>, parallel to FSE, and its velocity therein =. 

C x LH ; the velocity of P therefore, in the direction of the 

1 • H ^ 0 | • 

great circle OP, which is perpendicular to S in ? 

and along the great circle BP its velocity =0. 

T * t -7 P R O P O- 


5°P 


Mr . Wildbore on 


PROPOSITION II. 

Supposing the centre of a fphere to be at reft, whilft the 
furface moves round it in any manner whatfoever ; then, if the 
fame invariable point O, confidered as the pole of an axis of 
the fphere, be itfelf in motion, the angular velocity of the 
fpherical furface about that axis will be unequable, or that of 
one point therein different from that of another. 

For, let I (fig. 2.) be the centre of the fphere; draw the 
great circle POF perpendicular to the direction of the motion 
of the furface at O; then mud the pole of this motion necef- 
farily be in fome point P of this great circle POF. Let FC 
be the great circle whofe pole is P, and LQ that whofe pole is 
O ; then, the velocity of any point F of the great circle FC 
muft, by the preceding propofition, be equal to that of any 
other point H thereof. Let that velocity be reprefented by the 
equal arches FG and HK, and from the pole O draw the great 
circles OGM, OHN, and OKA, cutting the great circle LQ^ 
in M, N, and A ; then muft LM reprefent the angular velo- 
city of the point F about the axis IO, and NA that of the point 
H. But, by Prop. 9. Lib. III. Theodosii Sphericorum, LM 
is greater than NA ; and confequently the angular velocity of 
the point F about IO is greater than that of H ; and confe- 
quently the angular velocity of the furface about the axis lOis 
unequable. 

Corollary . Hence, about whatever axis the angular motion of 
a fphere is equable, the pole of that axis, and confequently 
the axis itfelf, muft be at reft at the inftant. Different motions 
may have different correfpondent poles, and confequently, 
when the motion is variable^ the place of the pole of equable 

motion 


Spherical Motion. 501 

motion on the furface may vary ; but whatever point on the 
furface correfponds with that pole muft at the inftant be at 
reft. 

PROPOSITION III. 

Let ABC (fig. 3.) be an o&ant of a fpherical furface in mo* 
tion, while the centre is at reft ; and let the velocity of the 
great circle BC in its own plane = a, and in a fenfe from B 
towards C ; that of C A in the fenfe from C towards A — b, 
and of AB from A towards B = c. If thefe three velocities 
a, b t and c, be conftant, the fpherical furface will always re- 
volve uniformly about the fame axis of the fphere at reft in 
abfolute fpace. 

For, let ABC, abc, be two pofitions of the revolving o&ant 
indefinitely near each other, A a, B b, and C c, the tracks of A, 
B, and C, in abfolute fpace. Perpendicular to ha draw the 
great circle SO A, and perpendicular to B b the great circle BOQ, 
cutting SOA in O and CA in Q.; then, becaufe A a is indefi- 
nitely fmall, the two triangles A pa right-angled at /, and a' Aq 
right-angled at A may be confidered as plane ones, and are 
therefore fimilar; and fince the angles pAQ and qAa are both 
right ones, taking away qAp, which is common, the angles 
pAa , qAQ , muft be equal; but as pA : pa :: c : b y likewife 
pA : pa f. pa A : L pAa, and paA=pAq 9 pAa — qAQ\ con- 

fequently, as f. pAq : ft qAQ c : b 9 that is, the fines of the 
angles BAS and CAS are proportional to the velocities along 
AB and CA; confequentlv, the fines of the arches SB and SC 
which are the meafures of thofe angles muft be in the lame 
ratio. In like manner it appears, that as ft CQ : ft AQ :: 


ij02 M?\ WlLDBORF, OH 

a : c :: ft CBQ : ft ABQ. Moreover, ft SOB : radius :: ft SB 
; ft BO :: ft AQ : ft. AO. Through C and O draw the great 
circle COR; then, as f. AO : radius :: ft. OAR : f. OR :: ft. 
OAQ : ft OQ, or f. OR : ft OQj: ft OAR : f. OAQ :: c : ^ 
and for alike reafon, f. OR : f. OS :: f. OBR : 1. OBS :: c : a, 
that is, f. OR : c :: f. OQ : b :: ft GS : or ft OQ : f. OS :: 

b : * ; but f. OQ : f. OS :: f. OCQ^= ft AR : f. OCSzzft BR, 
or f. AR : f. BR Now, be is ultimately perpendicular 

to AC in d , lo the triangle CJc being right-angled at d , the fum 
of the angles C cd, cCd muft be = a right one, and their lines are 
in the ratio of Cd : cd , or of b : a ; but the fum of the angles OCQ, 
OCS, is alfo a right one, and their lines alfo have been proved 
to he in the fame ratio of b : a, confequently the angle OCQj= 
Co/, and OCS = cCd, to GCS and cCd add the common angle 
OCQ, and the angle OCc muft be= BCQ a right one ; confe- 
quently OC is perpendicular to Cc the track of the point C, as 
OA is, by hypothefis, to A a, and OB to The fines of SO, 
QO, and RO, areas a, b , andc, alfo f. S 0 2 + ft QO' + f. RO 
by trigonometry = the fquare of radius = i ; hence f. SO -f- 
f. Qp 2 = i -ft R0 2 :rft CO 2 ; f. SO 2 q- f. RO^ftBO 2 , f. QO z 
+ f. RO 2 ^ f. AO 2 ; confequently, f. AO 2 , ft BO 2 and ft CO 2 are 
as ^ 2 + £% *r + c 2 , and a + b z , or as A a, B b z 9 and Cc 2 ; where- 
fore the velocities s/b z + c z , \/V + c 2 , and of the 

points A, B, C, are in directions perpendicular to AO, BO, 
and CO, and in the ratio of the fines of the arches AO, BO, 
and CO, that is of the diftances of the points A, B, and C, 
from the axis whofe pole is O, the tracks of thefe points are 
therefore circles of the fphere whofe radii are thole diftances. 
And fo long as the velocities a, b, and c, are invariable, the 
paints Q, R, and S, which are always at the fame diftances 
3 ' - from 


Spherical Motion . 503 

from B, C, and A, mull be always at the fame distances from 
O, that is, OR, OS, and OQ, are conftant, and the point O 
at reft. And this muft alfo be the cafe if a , b , and c be 
variable, provided they have the fame conftant ratio amongft 
themfelves. ' 

Corollary . Hence the points Q, R, and S, are the nodes of 
the great circles GQA, ARB, and BSC. 

Scholium . The demonftration of this proportion being thus 
ftriftly given, fomc notion may be obtained of the manner in 
which the point O 'varies its place upon 1 the fpherical furface 
when the velocities along the circles AB, BC, and CA, are va- 
riable. Thus, let fuch fpherical furface, fo revolving, receive 
an inftantaneous impulfe, at the diftance of a quadrant or go° 
from S, in a direction perpendicular to the plane of the great 
circle CSB ; then, the centre of the fphere may be kept at reft 
by an equal and contrary impulfe at this centre ; and finee, by 
hypothefis, the impulfe is given 90° from S, and in a direction 
perpendicular to the plane of the great circle CSB, it can nei- 
ther alter the place of the node S upon the circle, nor the ve- 
locity in the diredlion of its periphery, but only thofe in AB 
and CA. Thus, if the velocity in BA which before was = r 
be now equal to z; then, as f. SB : % f. SC : the velocity 
along CA, let this==y, whilft ftill the velocity along CB con- 
tinues as before™^ ; and this will caufe the point O to fall upon 
another point of the great circle SA : fo that whereas before 
the fines of OS, OR, and OQ, were as a, c 9 and b 9 they (hall 
now be as a 9 and y* Confequently, as f. SO : rad.n 1 a : 
the velocity at 90® from O, f. OR : 1 :: % : the velocity at 90° 
from O, and f. OQ :y :: 1 : velocity at 90° from O, which 
three quantities muft therefore be equal to one another, and to 
the angular velocity of the fphere about the axis whofe pole 


is 


Mr. Wildbore on 

is O; let this angular velocity — e, then mull ext S 0=a, 
ext. OR = s, and e x f. GQ=y, and the hum of the fquares 
of thefe three, or a 2 — e 2 x 1. SO + e x f. RO ! + f x l 
f.QQ z = e 2 , becaufe f. SO' + f. RO + f. QO =i, hence e = 

^/a" + z* +y z ; whereas, before the impulle e- ^/a r 4- b z + r. 
Thus not only the place of O, but, if z +jy be not = S + c , 
the angular velocity of the fphere about its lingle axis will alfo 
be altered. Hence then if, inftead of an inftantaneous im- 
pulfe, a motive force be fuppofed to ad in the fame diredion, 
and meafured at the fame point where the impulfe was juft 
now fuppofed to ad ; fuch force can neither vary the point S 
nor the velocity a, but will in time vary b and c, and caufe the 
point O to alter its place in SA ; and thus the velocities b and c 

will vary to y and z, and e — + b + c tor — \/ ’ & -ty + s » 

juft as it would have been by a fingle impulfe, excepting that 
then, when the impulfe was over, y and z muft have become 
conftant quantities, whereas now they will vary perpetually 
during the time that the motive force ads, and the point O 
will fhift its place fo as at different times to coincide with dif- 
ferent points of AS, though at any one inftant the point 
of the furface that coincides with it muft be at reft, by 
Prop. 2 . 

PROPOSITION IV. 

If a fpherical furface, whofe center is at reft, revolve in any 
manner whatfoever, fo that the velocities along the three qua- 
drants bounding any odant thereof be exprefled by any three 
variable quantities x, y, and z ; to find the neceflarily cor- 

refponding accelerating forces with which the place of the 

natural 


Spherical Motion, 505 

natural or momentary axis, and the angular velocity of the 
furface round it are varied. 

Here, other things remaining as in the preceding propofmon, 
inftead of the conftant quantities a , b, and c, we have the 
variable ones x, y, and z. Let the variable fines and cofines of 
AO, BO, and CO, be refpeaively expreffed by b and /3, g and 
7 , a’nd d and 5 ; and let t = the time from the commencement 
of the motion ; then it is well known, that the reipective 
accelerating forces along CB, CA, and AB, muft be expreffed by 

*:, i, and % ; and the radius of the fphere being fuppofed = 

i t i 

unity, the angular velocity about the axis whofe pole is 

z=y 9 e'Szzz, 


O = e ~ s/ x z + y -f-z 2, = es/ + y + § , efi — x 9 
# = 40 + fie 9 y ~?y + ye* $e, £T + y 4* = i > + 7r + ^ 

= 0, ( 3 ! +y=i = & +? = 1 r+r~: -£ 

-V, i= p£^+tf+li=^= j f5=^. A "‘>. 

V -x 1 -\-y + z 

by fpherics, as g : 1 :: l ■ *- = f- OBR=f. QA :: (2 : - = 1. OBS 
={. CQ=cof.AQ, tang. AQ = ^ and the fluxion of the arc AQ = 

^ g u t by the foregoing proportion, BO is perpendicu- 

lar to B b the track of the point B; confequently, as f. OBR 
_£ aQ^: f. OBS = cof. A Q :: z : x; therefore the tangent of 

. rv « j a xi~zi _ <Sxd'+av— ^x?g+>_ ag p £ f ore 

AQ= - and AQ =-*—*- e 2 +f 

therefore, whether e be conftant or variable it makes no differ- 
ence in the expreffion for AQ, In like manner it will appear, 

_• yi—xi V&—&Y 1 pc _ z j—y z _ Moreover, as 

that BR aad " b “ 7+i 5 “ / + r- 

rad. 


1 Z /02 1 . 2 

x -\-y P +? 

Vol. LXXX. 


yT + & 

u u u 


» 


^c6 Mr. Wildbore on 

rad. = I : the alteration of the place of Q round B, or in the 


&—*(3 


^/ 5 a + S a 


= the 


great circle AC = AQ : : f. BO= t g'=v / ,o -fo' : 

momentary alteration of place of O round B, or in a direction 

perpendicular to the great circle BOQ at O, and the cor- 

• • • 

refponding alteration of BO, that is, BO= — — vjL. ~ =* — - , 

the fluxion therefore of the track of O upon the fpherical 

hz]z— 20&UPP + V* /,3 2 k- + 

furface = \j = \J WZF~ 




4 


g 

-f 3 2 y 2 -f 1 2 y 2 -\-B 2 B 2 + 2$Soi-b c 2 i 5 


2 i 2 


/ 5 a + 


V^’+/ 3 2 + 7 • Again, 


the accelerating force in BA = - refolved into the direction of 


the great circle BO at B is ^ x cof. OBR =" * - , and that 

g 

• ^ 

~ along BC refolved into the fame diredtion is r x - , and the 

t t g 

difference of thefe, or the accelerating force in the direction 

BO in the fenfe from O towards B = — ~t — — _ — 

i* g* 


0 *— t 


e x — — ; in like manner that along CO in the fenfe from O 

<b 


towards C =: = e 

dt 

c>v — 


X 


yB — By 
dt 

$y—~y$ 


and that along OA from O 


towards A = y e x - y J — ; and as f.ROA (fig. 3.) —f, CO A 

— y d : 3 :: this laft mentioned force : ae x one equiva- 

lent thereto, but adting perpendicular to CO, and urging from 
O, that is, drawing the great circle DOE perpendicular to 

then, as 1 : f. DOC = f. ROE = " :: this laft force : the 

fame 


Spherical Motion . S°7 

fame reduced into the direction OE=eSx j~ a< ^‘ n g P cr * 
pendicular to the great circle BO, and in the fenfe from O / 

towards E : the fame force reduced into the diredion of the 

great circle BO at O is = e/3 x hzzji in the fenfe from O towards 

Q : in like manner is found a force equivalent to that in CO, 

but ading perpendicular to , which reduced 

into the diredion OD is = rj3 x y -t±L in the fenfe from O to- 

O 

wards D; but this fame force perpendicular to AO, when 

reduced into the diredion BO, is — eS x — — in the ienfe from. 

£y t 

O towards Q, which being added to the other above found 

ii i n i*i * T * * 

. r> rN • f d 1 y. yfj — X v ^ — I- 1 1 ’icrr— 

force in BO gives — — j — = - e x tne acce- 

lerating force ariling from thole which ad at O along the great 
circles OA, OC, which force ads in the fenfe from O towards 
Q, and therefore in a contrary fenfe, that is, from O towards B it 

mull be = e x as before found, the operation thus proving 

gt 

itfelf. In like manner, from the two forces now found, which 
ad perpendicular to OB at O, there muft arife one ading along 
OD in the fenfe from O towards D, which will therefore be = 

= L. X yfife - j3/Sy - Sty + j X - yy - 

g^ g^ 

ft 2 • - # This laft force may be otherwife found thus, 

/ / gi 

the acceleration =j/ round B at Q, and as i • g y : gy — the., 
acceleration round B at O owing to y 9 in like manner, the 
acceleration round G at O owing to z is ~ dz 9 which refolved 

U u u 2 * nta 


» 


ro8 


Mr. Wildbore on 


into the direction perpendicular to HO at O is— dz x f. ROE=* 
, alfo the acceleration bx at O perpendicular to AO reduced 


g 


into the direction perpendicular to BO = bx x f. DOS = 
, hence the whole acceleration along DE at O, which ma- 


b AO 


y@x 

g 

nifeftly arifes from thefe three, is — — — —gy, and the acce- 

g g 

lerative force — which, properly reduced, becomes — 

g t 

~ as before. And the force which is compounded of the two 

gt - j 

forces e x ^ and - % is = % V “fiS - 4- y ' = ^ + y + <5* 

gt g i g t 1 

adting perpendicular to the track of O upon the moving fpheri- 

cal furface; and - — f S ' x + is the accelerating force adling 

along the midcircle, or that which is 90 diftant from O, to 
alter the velocity about the natural or momentary axis whofe 
pole is O. Hence, anfwerable to the three accelerating forces 

P * rv> 

and - , round the axes whofe poles or ends A, B, and C, 

i t i. 

are always the fame invariable points upon the moving fpherical 
furface, there arife three other accelerating forces, namely, 

e x , and fe-t ; the two former adting at the 

gt 7 gt t 5 

pole of the momentary axis, and the latter is that whereby the 
velocity about the momentary axis is altered. 


scholium 1 . 


From the preceding inveftigation of the forces e x and 


gt 


* it follows, that they are not at all affedted in expreffion by 


the 


Spherical Motion . 5° 9 

the variation of A but are denoted by the fame quantities, 
whether e be conftant or variable ; which conclufion, and alfo 
the values of the forces themfelves, is perfedtly agreeable to 
what is brought out by Mr Landen, by a method fo very 
different, in the Philofophical Tranlaetions for 1777. 

But it is here carefully to be noted, that thefe are not motive 
forces, but accelerative ones ; for no notice whatever is yet 
taken of the internal ftructure of the revolving globe ; but the 
expreffions hold true, be that ftruaure what it will : if it be 
fuch that one and the fame quantity, drawn into each accele- 
rating force, will give the correfpondent motive one, then are 
the motive forces proportional to the accelerative ones, but 
otherwife not. It may here alfo be obferved, that it is quite 
conformable to nature, that thefe accelerating forces fhouid be 
exprefied by the fame quantities whether e be conftant or va- 
riable ; for thefe forces, adding at the pole of the natural axis, 
cannot poffibly have any effeft upon the velocity round it. But 
it is not hence by any means to be concluded, that the velo- 
city about the axis is therefore conftant ; becaufe thefe are not, 
in general, the only accelerating forces that add upon the body, 
but there is alfo a third accelerating force whofe value Is 

arifing from the different variability of x, y, and z, and 

which cannot vanifh except @x + yy + $z = o, it therefoie can 
only vanifh in particular cafes. 

If the equation e~ @x + yy + $z be fquared, there will 

thence arife after due ordering e z = x +f + z‘ - e X 

( yl Q - where the member which is 

drawn into e keeps its form whether e be conftant or variable, 

but by no means will x z +y+z\ after due fubftitution, do fo 

2 too. 

D 


$to Air. Wildbore on 

1 • 

too. If £ — o, then e z =x* +f + z\ the motion being then 
round what M. Euler and M. d’Alembert call the initial 
axis, or that about which the body at reft would be firft ur^ed 
to move by any external forces adting upon it ; and which they 
have determined with fo much labour; though here it follows, 
as a necefi'ary confequence, that the force with which the bodv is 

turned round this initial axis is= or a force ~ 

\ r t t 

the fum of the forces round the axes vvhofe poles are A, B, 
and C. 


\q 

Moreover, by the general laws of all motion, — — — , — - , and 

. . 

m * • • 

I I 2 j i I 

/ - — are the velocities with which the pole of the mo- 


mentary axis fhifts its place in directions perpendicular to 
BO, along BO and along its own track on the lurface refpec- 
dlively. And it is by taking the fluxions of thefe, and 
dividing each fluxion bv that of the time, that the acce- 
lerating forces are had, which are due to fuch alteration of 
place of the momentary pole ; and thefe muft by no means be 


confounded with the forces before found— —and -X/Go — <?/3 

g t g* 

in thofe diredtions, thefe laft pertaining to the tendency of the 
lurface itfelf to motion at O, and the others to the fhifting 
of the pole of the axis upon the furface, which are different 
motions, as will more clearly appear from what follows. 

The preceding general properties of motion obtain in all 
bodies revolving round a center at reft, be their motion ever fo 
irregular; the three great circles bounding an odtant of the 
fpherical furface revolving with the body are alfo taken ad libi - 
turn, being any fuch circles whatever upon the furface ; and . 
hence the following very important confequence is drawn, viz* 

* ¥ 


Spherical Motion . 5 1 1 

2 / be in motion , sr put in motion , injlanianeous 

impulfe or otherwife, about its center of gravity at reft in ahfolute 
fpace , //^ by any means, Ihe accelerating forces acting along the three 
great circles bounding any octant of a fphertcal furface that has 
the fame center of gravity and revolves with the body 9 can be 
found , thofe acting at every other point of fuch fur face will necef- 
farily follow as natural confequences of thefe three f and thus all 
the motions of fuch body will be abfolutely determined . 


SCHOLIUM 21. 


As the above conelufions are exceedingly general, in order 
to form a diftindt idea how fuch furface moves, it may he pro- 
per here to illuftrate it by a particular example. Let then the 
velocity x be fuppofed conftant, and alio the angular velocity e ; 
then, from what is (hewn above, fines xx = o, e z = x 2 -\-y z -f z 

=:e z x (3 Z + y % + <T, ee—yy + — e x yy+SS, yy + So = o» 

• 1 \ ' 

13 = 0 , (3 a conftant quantity, therefore b is conftant, and the 
track of the point O upon the furface is a lefler circle of the 
fphere at the conftant diftance AO from the invariable point A 
of the furface, the radius of fuch lefter circle being — b~ ft AO 
(fig. 4 .), alfo y 2 -\-z — the conftant quantity e — x = e — e z (3 z == 

e 2 b 2 ~ze 2 x y'f-T, zz" ~yy y SS= — yj — 


y— • with which the pole O 
__ h 2 h-\ -y4 z cl b\ eo 

I V” 


b_l 

yi 


and the velocity 
fhifts its place — 

But ftill an expref- 


\ P \ ft* yi i V J 2 —!' 2 ' 

lion for t is wanting ; to the two preceding data it is therefore 
neceflary to add a third, which may be that the velocity with 
which Olhifts its place in the circle EOF is alfo conftant. Which 

will 


1 


c j 2 Mr . Wildbore on 

will come to the fame as a cafe occurring hereafter, when 
_. 0 y — % = — where A is fome conftant quantity ; 

for then x = o = e^ + f-e ee - xx +yy + zz=yy + z^ = eyy -f eoz, 
e = yy + Sz= + ^ = £ * -7& + 7& S = 0 > therefore <? is 

conftant, and i = — = 4 ^= 4~* and fince e~o, and x = e& + 

7 xy e py etfy 

£e = 0 = e@; therefore /3 = o, /3 conftant, and y=\/ b"' -f \ 

therefore i = ~ » and * = 3 g * arc EO ; confequently, 

the velocity with which O Ihifts its place in the arch EO is = 

‘It . which is a conftant quantity. 
a ’ 

proposition V. 

The fame being given, as in the laft propofition, it is pro- 
poled to illuftrate the manner in which the furface moves with 
refped to a point at reft in abfolute fpace. 

Let Z (fig. 4 .) be a point touching the furface, but at reft 
in abfolute f^ace whilft the furface moves under it in any man- 
ner whatfoever. In any one pofition of the oCtant ABC 
through Z draw the great circles As, By, and Cr, which by 
the property of the fphere muft be perpendicular to BC, CA, 
and AB, refpe&ively ; then muft the velocities of the fpheri- 
cal furface at s , y, and r, in directions perpendicular to each 
of the circles As, By, and Cr, be x, y , and s, the angular 
velocities therefore about Z, with which the furface paffes 

under s, q, and r, muft be — , JL-, and f -^-; throughZand 

O draw the quadrant of a great circle ZY ; then, as/3 : x : : f. OY 


Spherical Motion . 51^ 

\ e x f. OY = the velocity of the moving fpherical furface at Y> 
which is therefore the angular velocity of the furface at Y 
round an axis at reft whofe pole is Z, becaufe ZY^po 0 
which four values obtain, let the point Z be taken at reft in 
abfolute fpace wherefoever it will. Alfo, e x ft OZ is the ve- 
locity with which the furface pafles under Z in a direction 
perpendicular to the great circle OZ at Z, which mu ft there ^ 
fore be the real velocity of the furface itfelf there at that in- 
ftant; therefore the fluxion of the track upon the furface 
which continually pafles under Z is = e x L OZ x / = 

\/f. Zi 2 + ft Z^ 2 +f. Zr z From which equation, and the pro- 
perties of O found in the preceding propofitions, general ex« 
prefiions for the relation of Z and O may be obtained. But, 
feeing that there is fuch a latitude in determining or fixing 
upon a proper point Z out of an infinity of points at reft, and 
this handled in a general manner will run into a complex cal- 
culus ; in order to fix upon a point Z under the moft eligible 
conditions, it may be beft to deduce them from the properties 
of any particular problem that comes under confederation. 

For example, taking that in the fecond fchollum to the laft 
propofition, where # and e are conftant, and y + — x is 

alfo conftant and = e l y + e'T — e 7 — e 7 (¥ = off, or y 4- T = b 7 alfo 
conftant ; and the velocity with which O fluffs its place along its 

in 

proper track ■= Lz , conftant alfo. Here, in order to fix upon 

a proper point Z, fuppofe the motion to begin when O (fig. 5.) 
is upon the great circle AB at E, and after fome determinate 
time = t, fuppofe the oftant ABC to have arrived in the pofi- 
tion A / B / C / , and that in this time the point O has ftiifted its 
place from E to O, that is, fuppofing the oiftant ABC to be at 
reft in abfolute fpace, while A'B'C - ’ is in motion, on A'B 
Vol. LXXX. X x x taking 


• * 


514 iM>. WiLDBORE on 

taking A y ^=:AE, the point O will have fhifted its place in the 
time /, in abfolute fpace from E to O ; and upon the moving 
fpherical furface from e to O along a lefs circle whofe radius is 
equal to the fine of AE = f. A!e~{. A O ~ b. Now, at the 
commencement of the motion, that is, at AB, the firft velo- 
city of the point A along CA is e x f. AE = eb = the then value 
of y, becaufe the pole of the natural axis of motion E being 
then upon AB, the value of 2 = 0, and the pale E fhifting its 
place in the fenfe EO in abfolute fpace, and the invariable 
point A of the fpherical furface moving in the fenle AA% there 
mu ft be fome point Z between E and A at reft with refpeft to 
both thefe motions, or round which both of them may be 
fuppofed performed ; its property muft then be fuch, that as 
f. AZ : f. EZ :• velocity of A ~eb : to the velocity with which 

jP !EZf 

the pole E begins to fhift its place = eb x ; but is the 

velocity with which it fhifts its place upon the moving fpheri- 
cal furface at E about the radius = f. AE m f. AZ + EZ. And 
when O is at E the velocity with which the fpherical furface 
pafles under Z will be e x f. EZ. Again, when O is the 
place of the momentary pole, the velocity of the point A' =z 

s/y -f % = eV y 4- <T = eb as before, and the velocity with which 
O fhifts it place round A' as before ; it therefore fhifts its 

place round fome point Z in abfolute fpace fuch that eb x f~£z, 
ftill the velocity with which it fhifts it, which, becaufe A O = 

V 

AE, muft be the fame velocity and the fame point Z as before. 
Confequently, the point O fhifts its place along a lefler circle 
of the fphere whofe radius ^ f. EZr=f. OZ, and in the time of 
fuch fhifting from E to 0 ? or from A to A 7 , the point of the 
2. furface 

^ ' 


Spherical Motion* 5 1 ^ 

furface which at firft was under Z will arrive at s in Aft? 7 ’ 
where A's=AZ, and E confidered as the fame invariable 
point of the furface will arrive at e, fo that A^izAE; there* 
fore, fince EZ = OZ is conftant, and Z at reft both with 
with refpedt to the velocity eb of A / round it, and the velocity 

— with which O fliifts its place, itmuft be as f. EZ — f. OZ : 


f. AZ :: ^ : eb :: £ : 1, but b and /3 are the fine and cofine of 
AE = A'Q— EZ + AZ ; therefore, as f. EZ = b x cof. AZ — /3 
x f. AZ : |S x f. AZ :: I : r, and as b x cof. AZ : @ x f. AZ :: 

A 


I + r : 1 :: 4 - — tang* AE * tang* AZ 2= | x — - 

A 0 ° & £ A-f 1 


, and f. AZ : 


cof. AZ — f. BZ :: : A-f x x /3 :: tang. AE * f. AZ 


A 


A£ 


— 9 and cof. AZ = -£===. ; and thus a dif- 

^A a + *A|S»-i-jS* + 

tin£t idea of this motion of the fpherical furface is obtained, it 
being now clear, that the point A / moves round Z at reft 


with the velocity eb , and as f. ZA : 1 : t eb : 


e i SA* + 2 A0 z ±I3 & 
A 


the angular velocity with which A / moves round the axis 
whole pole is Z, which is therefore conftant * and at the fame 
time the furface itfelf moves in the direction of the great circle 
B C 7 , that is about the axis whofe pole is A 7 with the conftant 
velocity x — e/ 3 , which two motions may be confidered as fepa- 
rate, and the reft as confequences of them ; that is, the point 
Z is at reft, and the point A 7 moves uniformly round it, whilft 
the furface upon which A / is an invariable point moves round 
the axis whofe pole is A 7 with an uniform angular velo- 
city, thefe two angular velocities being in the ratio of 

X x x 2 K / 


Mr . YVildbore an 


516 

✓g + aAf + g . ^ or of v/a^ + a+D* x /3 2 -: A/3 ; therefore, 

the times being inverfely as the velocities, as A/3 : 
</A z -f- 2 AIT 4- /3 2 : : the time of one revolution of A' round 
Z : the time of one revolution of the furface round A 7 , that 
is, round the axis whofe pole is A', which time is given be- 

caufe xzzefi, and confequentiy the time of one revolution of 

eb3 

A' round Z is given. Again, e x f. OZ = ~ the 

velocity with which the furface pafles under Z (at reft). The 
angular velocity round the axis whofe pole is 0 = e, and the 
velocity round O in a circle whofe radius is bzz be^ O fliifts 
its place in a circle of the fame radius b with a velocity = 

— ; the time therefore in which O fliifts through the lefler 
A 

circle eO is to that of one revolution round O (which time 
may be fuppofed given) = T as eb :: or as 1 : that is, as 

- : 1 :: T ; — — the time in which O makes one revolution 
A £ 


T 

upon the furface. And as e/3 : T :: e : — =the time in which 

the furface makes one revolution round A\ or the axis whofe 
pole is A' ; and from the analogy above, the time of one revo- 
lution of A" round AT - Alfo, as 1 : f. AZ :: 

eB : — — = the velocity with which the furface would 

V A z + 2 A& z -\-$ z 

pafs under Z, owing to the motion only round the axis whofe 
pole is A\ and in a fenfe from W towards C ; whereas, owing 
to the compound motion it really moves under Z in a contrary 

fenfe with the velocity - ; this is, however, only a 

J VA z + 2A& z -\-8 z 

neceflary conference of the centres of the circles whofe radii 


are. 


Spherical Motion. 517 

are f. A'Z and f. EZ lifting their places in abfolute fpace, 
which therefore can in no wife affeft the velocities round thofe 
centres, which velocities muffc ftill be the fame relatively to 
the centres as if the centres were at reft. Hence, then, the 
nature of this fpherical motion is fuch, .that the axis whofe 
pole is Z being abfolutely at reft, the pole O fo fhifts its place 
in a circle whole radius ZO alfo at reft, as to do fo with a 

conftant velocity = eh x the velocity with which it 

J i. AZ~~ A 

fhifts its place in the circle eO on the moving furface, the 
track therefore on the moving furface oiculates or rods upon 

that on the immoveable one. Therefore, fince — = the time of 

one revolution of O upon the moving furface, and the time 
of one revolution of A' 3 and confequently O round Z = , 

.. -- ; in the time of one revolution of O on the 

moving furface, it will have fhifted its place round Z in the 
circle whofe radius zzz f . OZ, through an arc — the whole peri- 

phery x + ? that is, it will have made + aA + 1 

o'* 

revolutions round Z : for, as the two circles eO and EO ofcu- 

late, it will take + 2 A + 1 times the periphery of 

EO to go round eQ, that is, the point A\ and confequently O 
will have moved this number of times round Z at reft, whilft 
O fhifts its place once round the fpherical furface in motion. 
Hence then the nature of the motion round the momentary 
axis whole pole is O, and the fixed one whofe pole is Z, will 
be apparent from the following iimple contrivance. A circle 
EO to radius = f. ZO-f. ZE being drawn upon a v fpherical 

furface at reft, an odtant of which is ABC, let a paper, or 

other 


5 1 B • - Mr . Wil'd bo he on 

other loofe furface, be fitted to this ochnt, and having on the 
centre A and radius AE deferibed a circular arc on the loofe 
furface, let the part thereof EOFCBE be cut away, and 
completing the circle EF of the remaining part, let the cir- 
cumference of this circle be moved uniformly along the cir- 
cumference of the lefs fixed circle EO with the celerity 

^ beginning at the point E in each, fo that the moving circle 

may roll along the fixed one, that is, fo that the arc Oe of 
the moving circle which has been in contaft with the fixed one 
may be always equal to the arc EO of the fixed one with 
which it has been in contaft ; then, fince OZ and ZA 7 arc 
conftant, and OZ perpendicular to both circles, the point A 7 
muft deferibe upon the fixed furface, the fame locus as in the 
cafe of the motion above fpecified. The locus alio of the mo- 
mentary pole O will be the fame, and the angular velocity of 
A 7 about the momentary axis the fame as that of the moving 
fu rface about it : for the celerity of O about the axis whole 

poleisZ = ^ being equal to the celerity about A 7 in motion, 

and the locus of A ' being a circle whofe radius = f. ZA, we 

have, as f. ZO : f. ZA 7 :: ^ : ^ = the velocity of A 7 , and as 

f OA ' : eb :: radius = i : £=zthe velocity about the mo- 
mentary axis, as it ought. 

From this complete folution of the particular cafe may be 
collected in general, that if the odlant ABC be taken fuch 
upon the moving fpher’eal furface, that the track of O there- 
upon may crofs the two great circles AB and AC at right 
angles, a point which is at reft with refpect to both motions, 
or round which they are performed like a fingle motion, may 
at the inftant of the momentary pole’s crofting each of thofe 

great 


Spherical Motion . 5 r y 

great circles be found, in the fame manner as in the particular 
cafe here ipecified. And it will alfo be found for any pofition 
of O, by means of the expreffions for the velocities found in 
Scholium I. Prop. iv. ; but of this more hereafter. 

PROPOSITION VI. 

If a parallelopipedon (or other * folid) revolving uniformly 
with an angular velocity =# about one of its permanent axes 
of rotation, receive an inftantaneous impulfe in a diredlion pa- 
rallel to that axis, the centre of gravity of the body being 
fuppoied to be kept at reft by an equal and contrary impulfe 
given to it, and no other force adting upon the body, it is. 
propofed to determine the alteration in the motion thereof,, 
in confequence of fuch inftantaneous impulfe. 

The impulfe being, by hypothefis, given in a diredlion per- 
pendicular to that of the then only motion of every particle of 
the body, cannot inftantly alter its angular velocity about the 
permanent axis ; but its immediate effedt muft be to caule the 
body to revolve about a frefh axis, whilft the angular velocity, 
and confequently the momentum of rotation about the firft or 
permanent axis, remain unaltered by fuch inftantaneous im- 
pulfe; for though it gives a different diredlion and velocity to 
the particles, by caufing them to revolve about another axis, 
yet muft their relative velocity about the firft remain unaltered 
by the nature of relative motion, becaufe the fecond or addi- 
tional motion is given in a diredlion perpendicular to the firft.. 
Any alteration therefore which may be made in the velocity 
about the firft axis, by reafon of the oblique motion of the 
particles about it, owing to the then revolution about a frefh 
axis, muft be a work of time. And to determine fuch alteration, 

% See the note (Cf at the end of the Paper, 


let 


r 20 Mr. Wildeore on 

let M = themafs or folidity, and 2 d 9 2 c 9 and 2 b y be the three 
dimenfions or length, breadth, and thicknefs of fuch parallelo- 
pipedon ; then it is known that the momentum of inertia 
round the axis on which the dimenfion 2 d is taken will be=r 


|Mx c 2 -f^ 2 , this being no more than the produfl of a particle 
of the body into the fquare of its diftance from luch axis, 
when integrated through the whole body, as is now too well 
known to need the repetition here. Let I (tig. 6 .) be the 
centre of gravity or of inertia (they being both one) of fuch 
parallelopipedon, IB the permanent axis on which the dimen- 
iion 2 c is taken, Cl that on which 2 b is taken, and a perpen- 
dicular to the plane BIC (of the paper) at I that on which 2 d 
is taken; then on the centre I defcribing the quadrant BSC, 
whofe radius BI or Cl may be fuppofed unity; if the body 
once revolve about this laft named axis with an angular velo- 
cityrz zz meafured along the great circle BSC, and no external 
force or impulfe a ft upon it, it is agreed and well known, that 
the centrifugal motive force round fuch axis will beziMsf x 

— — and always being equal in contrary direftions round the 
3 

axis can have no power to alter the place thereof ; but fuch 
motion and motive force continuing always the fame, the axis 
muft be at reft, and the velocity round it uniform for ever. But, 
if the body whilft fo revolving receive (as by hypothefis) an 
impulfe in a dir eft ion parallel to this axis, that is, perpendicu- 
lar to the plane of the circle BCI, and an equal and contrary 
one to keep the centre I ftill at reft, the faid impulfe being 
perpendicular to the motion cannot inftantly alter the angular 
velocity but will give the axis itfelf a motion in a plane 
perpendicular to BCI, and confequently about fome axis SI in 
the plane BCI, round which axis SI the centrifugal motive 

forces 


/ 


Spherical Motion, 5 % 1 

forces of the particles being no longer in equilibria , becaufe it 
is not a permanent axis (except in particular cafes) this oblique 
motion of the particles will in time alter the velocity %■. To 
determine then the value of the motive force caufing fuch alte- 
ration of z, let ML — 2d be a line parallel to the fide of the 
parallelogram which is a feftion of the folid perpendicular to 
the axis Cl, q the middle point of ML, p any other point 
therein, pm and qn two perpendiculars to the plane which is 
perpendicular to BCI and pafles through SI ; and from B let 
fall BN perpendicular to the axis SI : then, the point n muft 
neceffarily fall upon SI, becaufe the plane BSCI produced bi- 
fe&s the folid, join pn which is the perpendicular diftance of 
p from the axis SI ; let v— the velocity of the body at B per- 
pendicular to BI and to the plane BCI ( which is the fame in- 
variable one in the body, and that wherein the permanent axes 
BI and Cl are fituated) ; then, as BN ; v 1 : the angular 

velocity of the body about the axis SI = ^, and by the nature 

of all motion, as BN t v :: x v - the velocity of the 

point p round n, or of a particle of the body at p in the circle 
whofe radius is pn, confequently the centrifugal accelerating 
force, which is always equal to the fquare of the velocity di- 
vided by the radius of motion, is there = x v afting in the 

direction pn upon the axis SI, which may De refolved into two 
others, the one parallel to the plane SmJ, which can have no 
effect in a direction perpendicular to that plane, and the others 

■hi x pm = ^ - 2 x qn perpendicular to that plane, which drawn 

into a particle^ of the body at p gives p x qn x g^-, — the motive 
Yol. LXXX, Y y y * orce 


5*2 


Mr. WlLDBORE on 


force of that particle to move the plane Swl in a direction pa- 
rallel to BN, or about the permanent axis which is perpendi- 
cular to the plane SBI, and which value is the fame in what- 
ever point of ML the particle^ is fituated. 

Let GgR (fig. 7.) be a fedlion of the folid by the plane IBSC ; 
then, fince the motive force of a particle p of the body 

fituated any where in a line perpendicular to this plane at y is 

% 

p X qn x the motive force arifing from the dimen foil ML = 

2 d of the body will be=:2dfo 2 x LL, and asSI= 1 : 1 n :: 2 dv~ x 
J Bi\ 

: zdv x = the equivalent motive force adling at the 

Bi \ 2 BN n 

conftant diftance SI “ unity ; which mud: hill be integrated with 
the other two dimenfions of the body, becaufe every par- 

tide ^MjjxKRxjj. In order to which, let now / = 
s and t = the line and cofine of QlK = NBI=SC to radius 
unity, IR=:£, GK = c, KR = ,v, and qg=y; then will KI — 
x — b 9 Ky r -y — c, and as / : KI : : 1 : yl z= - — - : : s : QK =: 


~ x x — b ; hence, Qy = Ky — QK ~y - c — s - x x — b, and 1 : 

Qy : : s : Qn ~s x y - c — ~ xx — b \ \t : qn~t x y - c - sx x — 

and In = QT+Q« = ^ xy c-\-i x x — b ; hence qnxln — stx ’ 
y — 2 y c + c + f x y — c x x — b — / x y — c x x — b — st x x — b\\ 
which multiplied into zofy and the fluent making y only variable 
fo as to comprehend the whole body, whenjy — 2c — ^G,is = zdfst x 


— — zc x x - 2 ox + and this multiplied into x, and the fluent 

taken in like manner, will, when = 2<£ 7 be=- x djstx 

3 


Spherical Motion . 


c l b~¥c — M fst X - 


b % Mv z st 


3 1 ‘ 


x c z - b 


sv z M — 1 

— x - X C - t) 

t 3 


5*3 

but as 


£ B5 v :! f. CS«sj : j s=the velocity of the body at C 
perpendicular to Cl and to the plane BC1; let - = x now, and 

• b ~ the mo- 


ISAxy 


v py, and the preceding fluent becomes — 1 x c 

tive force acting at S along the circle BSC to alter the velocity 
% along that circle ; and if this be divided by the inertia 

^ x c z + b z along BC, it gives xy x p ~ (where i p that of 

the time) - the accelerating force afting along the circle BC. 
Now (this being referred to fig. 3.), for the fame reafon, as 
the two velocities x and y along BC and CA turn the body 
about an axis whole pole is R in AB, and thus caufe the pertur- 

bating motive force x c — b z above computed, muft the two 

3 

velocities x and % along BC and BA turn the body about an 
axis in CA whofe pole is Q, and proceeding 111 the very fame 
manner as before, the perturbating motive force thence arifing 

will be found = — x to alter the motion along AC, and 

3 

1 17 ® 

y . to alter the velocity jy about 


the accelerative one — i 


b + d 2 


the permanent axis whofe pole is B. Alfo, the motive force 




X ^ - c, and the accelerative one = - 


d'--S 


•2 I J- 

a + c 


Xyz = to alter 


the velocity x along BC. 


scholium 1. 


Having thus obtained the values of the accelerating forces 
and - (fee Scholium I. prop, iv.), the matter is now 

Y y y 2 brought 


-24 Mr, Wildbore on 

brought to an rffue, and the motions and times may front 
hence be computed. But it will be proper firft to fhew 
wherein, and why, thefe conclufions differ from thofe brought 
out by Mr. Landen. 

The three perturbating motive forces acting along the peri- 
pheries of the three great circles CB, CA, and AB, in fig. 3 . 

Prop. iv. are above found to be — x d 2 — c x yz, — X b — d x -rs, 

3 


M 


and — x S — b*x xy refpedtively, or their equals — * a - c X 
3 * 

e\L - x b 2 - d * i x e*/3S, and - x c - b 2 x //S y. And if we fup- 
3 3 

pofe the accelerations x 9 y 9 and z 9 to be reflectively propor- 
tional to the motive forces, the fum x +y + z mull: be propor- 
tional to the fum of the three motive forces, and xx +yy + %z 

_ . 

or its equal efix + Pyy + eSz muft be proportional to — X d z - c 

X xe z yS+ - X b 2 - a x X c 2 — b 2 x zefcy = x efiya x 

3 1 3 


iffT? 4 - b 7, -d 1 + c - tf that is as nothing ; confequently, ee =z 
x$l+yy + zz = o, in which cafe therefore e muft be a conftant 
quantity. Moreover, thefe quantities now mentioned as re- 
fpeftively proportional to one another, turning the equal ratios 

into equations 


d—c z x yz f x 


X xy d z — c z X eyo 


y 




tr — d l X 


_ S-b~x eHy _ _ De^ ^ Ce$y . henC£ D/3/3 = -B yy, 

i h y i 

* 

and DSo = — and taking the fluents of thefe two laft 
equations, putting n and m for the refpeftive values of (2 and $ 
when y~ o, we obtain D/3 1 = D n — and D<T = D m — Cy% 

confequently B — r— and o '= ; which are the 

very 


& 


Spherical Motion . 525 

very equations brought out by Mr. Landen in fo very different 
a manner. 

Here then the matter may be fafely refted ; for the accelera- 
tions are moft certainly as the accelerative forces, and not as the 
motive ones. Conclufions, therefore, that are drawn from a 
contrary fuppofition cannot be true. 

It may not, however, be improper to (hew here how Mr. 
La n den’s motive forces E and E /7 arife from thofe above 
brought out; thus, in fig. 3. Prop. iv. let s and t the fine and 

cofine of AQ to radius 1, that is, let s 

motive force along BA refolved into the direction BO becomes 

— x c A - X e*( 3 yt 9 and that along BG refolved into the fame 

diredion BO becomes — x a — c X cyh^ the difference of thefe 

3 1 


— and /= then the 

g g 


ss — x e z y x d 2 — c 2 x $s - c 2 - b L x $i = 

3 3 




X O/ — C muft be 


the motive force ading along the great circle BO in the fenfe 
from B towards O, or from O towards Q; and this is the very 
motive force E determined by Mr. Landen, and ading in the 
fame manner. The motive force which ads at O perpendicu- 
larly to the force E is moft readily obtained from that ading 
along CA ; for if a tangent be drawn to the great circle BOQ 
at O (fig. 3.) it will interfed a radius of the fphere drawn 

through Q at a diftance ( - j from I the centre of the fphere == 

the fecant of the arc OQ, and as 1 : - = that fecant :: the force 

g 

MD//3J 1 Tn r i ^ MV e 7, git 

ading at the diftance QJrom the centre : — — ~ - 

the force adting in the plane of the great circle CIA at the 

diftance - from the centre I, and perpendicular to a tangent at 
' O 


>ji6 Mr. Wildbore on 

0